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Sample records for gas sensors operating

  1. Field testing the Raman gas composition sensor for gas turbine operation

    NASA Astrophysics Data System (ADS)

    Buric, Michael P.; Chorpening, Benjamin T.; Mullen, Jessica C.; Ranalli, Joseph A.; Woodruff, Steven D.

    2012-06-01

    A gas composition sensor based on Raman spectroscopy using reflective metal lined capillary waveguides is tested under field conditions for feed-forward applications in gas turbine control. The capillary waveguide enables effective use of low powered lasers and rapid composition determination, for computation of required parameters to pre-adjust burner control based on incoming fuel. Tests on high pressure fuel streams show sub-second time response and better than one percent accuracy on natural gas fuel mixtures. Fuel composition and Wobbe constant values are provided at one second intervals or faster. The sensor, designed and constructed at NETL, is packaged for Class I Division 2 operations typical of gas turbine environments, and samples gas at up to 800 psig. Simultaneous determination of the hydrocarbons methane, ethane, and propane plus CO, CO2, H2O, H2, N2, and O2 are realized. The capillary waveguide permits use of miniature spectrometers and laser power of less than 100 mW. The capillary dimensions of 1 m length and 300 μm ID also enable a full sample exchange in 0.4 s or less at 5 psig pressure differential, which allows a fast response to changes in sample composition. Sensor operation under field operation conditions will be reported.

  2. Field testing the Raman gas composition sensor for gas turbine operation

    SciTech Connect

    Buric, M.; Chorpening, B.; Mullem, J.; Ranalli, J.; Woodruff, S.

    2012-01-01

    A gas composition sensor based on Raman spectroscopy using reflective metal lined capillary waveguides is tested under field conditions for feed-forward applications in gas turbine control. The capillary waveguide enables effective use of low powered lasers and rapid composition determination, for computation of required parameters to pre-adjust burner control based on incoming fuel. Tests on high pressure fuel streams show sub-second time response and better than one percent accuracy on natural gas fuel mixtures. Fuel composition and Wobbe constant values are provided at one second intervals or faster. The sensor, designed and constructed at NETL, is packaged for Class I Division 2 operations typical of gas turbine environments, and samples gas at up to 800 psig. Simultaneous determination of the hydrocarbons methane, ethane, and propane plus CO, CO2, H2O, H2, N2, and O2 are realized. The capillary waveguide permits use of miniature spectrometers and laser power of less than 100 mW. The capillary dimensions of 1 m length and 300 μm ID also enable a full sample exchange in 0.4 s or less at 5 psig pressure differential, which allows a fast response to changes in sample composition. Sensor operation under field operation conditions will be reported.

  3. Low temperature operated NiO-SnO2 heterostructured SO2 gas sensor

    NASA Astrophysics Data System (ADS)

    Tyagi, Punit; Sharma, Anjali; Tomar, Monika; Gupta, Vinay

    2016-04-01

    Sulfur dioxide (SO2) is among the most toxic gas released by the industries which is extremely dangerous for human health. In the present communication, an attempt has been made for the detection of SO2 gas (500 ppm) with the help of SnO2 thin film based gas sensor. A low sensing response of 1.3 is obtained for sputtered SnO2 thin films based sensors at a high operating temperature of 220 °C. To improve the sensing response, different heterostructured sensors are developed by incorporating other metal oxide thin films (PdO, MgO, NiO, V2O5) over SnO2 thin film surface. Sensing response studies of different sensors towards SO2 gas (500 ppm) are presented in the present report. Among all the prepared sensors NiO-SnO2 hetero-structure sensor is showing highest sensing response (˜8) at a comparatively lower operating temperature (140 °C). Possible sensing mechanism for NiO-SnO2 heterostructured sensor has also been discussed in the present report.

  4. Gas sensor

    SciTech Connect

    Schmid, Andreas K.; Mascaraque, Arantzazu; Santos, Benito; de la Figuera, Juan

    2014-09-09

    A gas sensor is described which incorporates a sensor stack comprising a first film layer of a ferromagnetic material, a spacer layer, and a second film layer of the ferromagnetic material. The first film layer is fabricated so that it exhibits a dependence of its magnetic anisotropy direction on the presence of a gas, That is, the orientation of the easy axis of magnetization will flip from out-of-plane to in-plane when the gas to be detected is present in sufficient concentration. By monitoring the change in resistance of the sensor stack when the orientation of the first layer's magnetization changes, and correlating that change with temperature one can determine both the identity and relative concentration of the detected gas. In one embodiment the stack sensor comprises a top ferromagnetic layer two mono layers thick of cobalt deposited upon a spacer layer of ruthenium, which in turn has a second layer of cobalt disposed on its other side, this second cobalt layer in contact with a programmable heater chip.

  5. A novel NO2 gas sensor based on Hall effect operating at room temperature

    NASA Astrophysics Data System (ADS)

    Lin, J. Y.; Xie, W. M.; He, X. L.; Wang, H. C.

    2016-09-01

    Tungsten trioxide nanoparticles were obtained by a simple thermal oxidation approach. The structural and morphological properties of these nanoparticles are investigated using XRD, SEM and TEM. A WO3 thick film was deposited on the four Au electrodes to be a WO3 Hall effect sensor. The sensor was tested between magnetic field in a plastic test chamber. Room-temperature nitrogen dioxide sensing characteristics of Hall effect sensor were studied for various concentration levels of nitrogen dioxide at dry air and humidity conditions. A typical room-temperature response of 3.27 was achieved at 40 ppm of NO2 with a response and recovery times of 36 and 45 s, respectively. NO2 gas sensing mechanism of Hall effect sensor was also studied. The room-temperature operation, with the low deposition cost of the sensor, suggests suitability for developing a low-power cost-effective nitrogen dioxide sensor.

  6. Highly sensitive and selective WO3 nanoparticle gas sensor operating in thermally modulated dynamic mode

    NASA Astrophysics Data System (ADS)

    Ionescu, Radu; Hoel, Anders; Granqvist, Claes-Goran; Llobet, Eduard; Heszler, Peter

    2004-05-01

    Nanoparticle films of crystalline WO3, designed for gas sensing applications, were deposited on alumina substrates by reactive gas deposition. H2S, ethanol vapour, and binary mixtures of ethanol/H2S, ethanol/NO2 and H2S/NO2 were used in different concentrations for testing the performance of the sensor device. The sensor was operated in dynamic mode by modulating its temperature between 150 and 250 °C. Coefficients were extracted by applying Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) methods to the dynamic resistance response of the sensor. These coefficients were then used as inputs for pattern recognition methods to extract both quantitative (concentration) and qualitative (chemical selectivity) information about the test gases. After sensor calibration, it was possible to detect as little as 200 ppb of ethanol and 20 ppb of H2S with good accuracy. Furthermore, ethanol and H2S could be detected with good sensitivity and selectivity in the presence of both reducing and oxidising gases.

  7. Microfabricated Formaldehyde Gas Sensors

    PubMed Central

    Flueckiger, Jonas; Ko, Frank K.; Cheung, Karen C.

    2009-01-01

    Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation. PMID:22291561

  8. Tuning operating point of extrinsic Fabry-Perot interferometric fiber-optic sensors using microstructured fiber and gas pressure.

    PubMed

    Tian, Jiajun; Zhang, Qi; Fink, Thomas; Li, Hong; Peng, Wei; Han, Ming

    2012-11-15

    Intensity-based demodulation of extrinsic Fabry-Perot interferometric (EFPI) fiber-optic sensors requires the light wavelength to be on the quadrature point of the interferometric fringes for maximum sensitivity. In this Letter, we propose a novel and remote operating-point tuning method for EFPI fiber-optic sensors using microstructured fibers (MFs) and gas pressure. We demonstrated the method using a diaphragm-based EFPI sensor with a microstructured lead-in fiber. The holes in the MF were used as gas channels to remotely control the gas pressure inside the Fabry-Perot cavity. Because of the deformation of the diaphragm with gas pressure, the cavity length and consequently the operating point can be remotely tuned for maximum sensitivity. The proposed operating-point tuning method has the advantage of reduced complexity and cost compared to previously reported methods.

  9. Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

    SciTech Connect

    Hierlemann, A.; Hill, M.; Ricco, A.J.; Staton, A.W.; Thomas, R.C.

    1999-01-11

    We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseous analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.

  10. Fiber optic gas sensor

    NASA Technical Reports Server (NTRS)

    Chen, Peng (Inventor); Buric, Michael P. (Inventor); Swinehart, Philip R. (Inventor); Maklad, Mokhtar S. (Inventor)

    2010-01-01

    A gas sensor includes an in-fiber resonant wavelength device provided in a fiber core at a first location. The fiber propagates a sensing light and a power light. A layer of a material is attached to the fiber at the first location. The material is able to absorb the gas at a temperature dependent gas absorption rate. The power light is used to heat the material and increases the gas absorption rate, thereby increasing sensor performance, especially at low temperatures. Further, a method is described of flash heating the gas sensor to absorb more of the gas, allowing the sensor to cool, thereby locking in the gas content of the sensor material, and taking the difference between the starting and ending resonant wavelengths as an indication of the concentration of the gas in the ambient atmosphere.

  11. A High-Sensitivity Gas Sensor Toward Methanol Using ZnO Microrods: Effect of Operating Temperature

    NASA Astrophysics Data System (ADS)

    Sinha, M.; Mahapatra, R.; Mondal, B.; Ghosh, R.

    2017-04-01

    In the present work, zinc oxide (ZnO) microrods with the average diameter of 350 nm have been synthesized on fluorine doped tin oxide (FTO) substrate using a hydrothermal reaction process at a low temperature of 90°C. The methanol gas sensing behaviour of as-synthesized ZnO microrods have been studied at different operating temperatures (100-300°C). The gas sensing results show that the ZnO microrods exhibit excellent sensitivity, selectivity, and stability toward methanol gas at 300°C. The as-grown ZnO microrods sensor also shows the good sensitivity for methanol even at a low operating temperature of 100°C. The ultra-high sensitivity of 4.41 × 104% [gas sensitivity, S g = ( I g - I a)/ I a × 100%] and 5.11 × 102% to 100 ppm methanol gas at a temperature of 300°C and 100°C, respectively, has been observed. A fast response time of 200 ms and 270 ms as well as a recovery time of 120 ms and 1330 ms to methanol gas have also been found at an operating temperature of 300°C and 100°C, respectively. The response and recovery time decreases with increasing operation temperature of the sensor.

  12. Effects of Operating Temperature on Droplet Casting of Flexible Polymer/Multi-Walled Carbon Nanotube Composite Gas Sensors

    PubMed Central

    Chiou, Jin-Chern; Wu, Chin-Cheng; Huang, Yu-Chieh; Chang, Shih-Cheng; Lin, Tse-Mei

    2016-01-01

    This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT) composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating temperatures (room temperature, 40 °C, 50 °C, 60 °C, and 70 °C) via impedance spectrum measurement and sensing response experiments. The selected polymers that were droplet cast to coat a MWCNT conductive layer to form two-layer polymer/MWCNT composite sensing films included ethyl cellulose (EC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Electrical characterization of impedance, sensing response magnitude, and scanning electron microscope (SEM) morphology of each type of polymer/MWCNT composite film was performed at different operating temperatures. With respect to ethanol, the response magnitude of the sensor decreased with increasing operating temperatures. The results indicated that the higher operating temperature could reduce the response and influence the sensitivity of the polymer/MWCNT gas sensor array. The morphology of polymer/MWCNT composite films revealed that there were changes in the porous film after volatile organic compound (VOC) testing. PMID:28025507

  13. Ultrasensitive Room-Temperature Operable Gas Sensors Using p-Type Na:ZnO Nanoflowers for Diabetes Detection.

    PubMed

    Jaisutti, Rawat; Lee, Minkyung; Kim, Jaeyoung; Choi, Seungbeom; Ha, Tae-Jun; Kim, Jaekyun; Kim, Hyoungsub; Park, Sung Kyu; Kim, Yong-Hoon

    2017-03-15

    Ultrasensitive room-temperature operable gas sensors utilizing the photocatalytic activity of Na-doped p-type ZnO (Na:ZnO) nanoflowers (NFs) are demonstrated as a promising candidate for diabetes detection. The flowerlike Na:ZnO nanoparticles possessing ultrathin hierarchical nanosheets were synthesized by a facile solution route at a low processing temperature of 40 °C. It was found that the Na element acting as a p-type dopant was successfully incorporated in the ZnO lattice. On the basis of the synthesized p-type Na:ZnO NFs, room-temperature operable chemiresistive-type gas sensors were realized, activated by ultraviolet (UV) illumination. The Na:ZnO NF gas sensors exhibited high gas response (S of 3.35) and fast response time (∼18 s) and recovery time (∼63 s) to acetone gas (100 ppm, UV intensity of 5 mW cm(-2)), and furthermore, subppm level (0.2 ppm) detection was achieved at room temperature, which enables the diagnosis of various diseases including diabetes from exhaled breath.

  14. Discriminating among different tea leaves using an operating temperature-modulated tin oxide gas sensor

    NASA Astrophysics Data System (ADS)

    Rastkhadiv, Ali; Jenabi, Amin; Souri, Asma

    2016-03-01

    We report distinguishing different types of tea leaves from each other based on their aroma using a thermal shock-induced generic tin oxide gas sensor. The sensor used in this work consists of a microheater and a tin oxide pellet, both connected to outside circuitry with noble metal contacts. The heater is powered with a series of narrow high magnitude voltage impulses of predetermined thermal impacts adjusted to produce step-like temperature rises of different magnitudes on the gas sensitive pellet. The sensor is exposed to aromas collected from various types of tea leaves at different concentrations. Within 4.5 s, nine 500 ms-wide voltage pulses, each as high as 9.3 V in magnitude, are applied to the microheater. Each pulse causes a step-like temperature jump on the pellet temperature. The transient responses recorded for different tea leaves look different even after amplitude normalization. The sensor profiles are recorded, digitized, and compared with the database of previous experiences. A heuristically defined high dimensional feature vector is automatically generated for each analyte. Classifications are graphically achieved in a 3-D feature space after applying principle component analysis for dimension reduction.

  15. Investigation of poly(o-anisidine)-SnO2 nanocomposites for fabrication of low temperature operative liquefied petroleum gas sensor

    NASA Astrophysics Data System (ADS)

    Patil, Dewyani; Kolhe, Kishor; Potdar, Hari S.; Patil, Pradip

    2011-12-01

    Poly(o-anisidine)-tin oxide (POA-SnO2) nanocomposites has been investigated for the fabrication of low temperature operative (100 °C) liquefied petroleum gas (LPG) sensor. The POA-SnO2 nanocomposites have been synthesized through an in situ chemical polymerization of o-anisidine in presence of SnO2 nanoparticles. The POA-SnO2 nanocomposite shows better LPG sensing properties than that of pure POA. The nanocomposite with 50 wt. % SnO2 exhibits an excellent LPG sensing characteristics at the operating temperature of 100 °C such as higher relative gas response (˜23.47% to 3.4% of LPG), extremely rapid response (˜6 s), fast recovery (˜33 s), good reproducibility, and remarkable selectivity. The application of POA-SnO2 nanocomposites for fabrication of the LPG sensor was demonstrated.

  16. Ultra-Low-Power MEMS Selective Gas Sensors

    NASA Technical Reports Server (NTRS)

    Stetter, Joseph

    2012-01-01

    This innovation is a system for gas sensing that includes an ultra-low-power MEMS (microelectromechanical system) gas sensor, combined with unique electronic circuitry and a proprietary algorithm for operating the sensor. The electronics were created from scratch, and represent a novel design capable of low-power operation of the proprietary MEMS gas sensor platform. The algorithm is used to identify a specific target gas in a gas mixture, making the sensor selective to that target gas.

  17. Gas sensor with attenuated drift characteristic

    DOEpatents

    Chen, Ing-Shin [Danbury, CT; Chen, Philip S. H. [Bethel, CT; Neuner, Jeffrey W [Bethel, CT; Welch, James [Fairfield, CT; Hendrix, Bryan [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

    2008-05-13

    A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

  18. Calorimetric gas sensor

    DOEpatents

    Ricco, Antonio J.; Hughes, Robert C.; Smith, James H.; Moreno, Daniel J.; Manginell, Ronald P.; Senturia, Stephen D.; Huber, Robert J.

    1998-01-01

    A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 .mu.m thick.times.10 .mu.m wide.times.100, 250, 500, or 1000 .mu.m-long polycrystalline Si; some are overcoated with a 0.25 .mu.m-thick protective CVD Si.sub.3 N.sub.4 layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac).sub.2 onto microfilaments resistively heated to approximately 500.degree. C.; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300.degree. C. (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H.sub.2 concentrations between 100 ppm and 1% in an 80/20 N.sub.2 /O.sub.2 mixture. Other catalytic materials can also be used.

  19. Calorimetric gas sensor

    DOEpatents

    Ricco, A.J.; Hughes, R.C.; Smith, J.H.; Moreno, D.J.; Manginell, R.P.; Senturia, S.D.; Huber, R.J.

    1998-11-10

    A combustible gas sensor is described that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 {micro}m thick {times} 10{micro}m wide {times} 100, 250, 500, or 1000 {micro}m-long polycrystalline Si; some are overcoated with a 0.25 {micro}m-thick protective CVD Si{sub 3}N{sub 4} layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac){sub 2} onto microfilaments resistively heated to approximately 500 C; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300 C (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H{sub 2} concentrations between 100 ppm and 1% in an 80/20 N{sub 2}/O{sub 2} mixture. Other catalytic materials can also be used. 11 figs.

  20. SiC-Based Gas Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak; Liu, C. C.; Wu, Q. H.

    1997-01-01

    Electronic grade Silicon Carbide (SiC) is a ceramic material which can operate as a semiconductor at temperatures above 600 C. Recently, SiC semiconductors have been used in Schottky diode gas sensor structures. These sensors have been shown to be functional at temperatures significantly above the normal operating range of Si-based devices. SiC sensor operation at these higher temperatures allows detection of gases such as hydrocarbons which are not detectable at lower temperatures. This paper discusses the development of SiC-based Schottky diode gas sensors for the detection of hydrogen, hydrocarbons, and nitrogen oxides (NO(x)). Sensor designs for these applications are discussed. High sensitivity is observed for the hydrogen and hydrocarbon sensors using Pd on SiC Schottky diodes while the NO(x) sensors are still under development. A prototype sensor package has been fabricated which allows high temperature operation in a room temperature ambient by minimizing heat loss to that ambient. It is concluded that SiC-based gas sensors have considerable potential in a variety of gas sensing applications.

  1. Temperature-programmed technique accompanied with high-throughput methodology for rapidly searching the optimal operating temperature of MOX gas sensors.

    PubMed

    Zhang, Guozhu; Xie, Changsheng; Zhang, Shunping; Zhao, Jianwei; Lei, Tao; Zeng, Dawen

    2014-09-08

    A combinatorial high-throughput temperature-programmed method to obtain the optimal operating temperature (OOT) of gas sensor materials is demonstrated here for the first time. A material library consisting of SnO2, ZnO, WO3, and In2O3 sensor films was fabricated by screen printing. Temperature-dependent conductivity curves were obtained by scanning this gas sensor library from 300 to 700 K in different atmospheres (dry air, formaldehyde, carbon monoxide, nitrogen dioxide, toluene and ammonia), giving the OOT of each sensor formulation as a function of the carrier and analyte gases. A comparative study of the temperature-programmed method and a conventional method showed good agreement in measured OOT.

  2. Flexible Transparent Electronic Gas Sensors.

    PubMed

    Wang, Ting; Guo, Yunlong; Wan, Pengbo; Zhang, Han; Chen, Xiaodong; Sun, Xiaoming

    2016-07-01

    Flexible and transparent electronic gas sensors capable of real-time, sensitive, and selective analysis at room-temperature, have gained immense popularity in recent years for their potential to be integrated into various smart wearable electronics and display devices. Here, recent advances in flexible transparent sensors constructed from semiconducting oxides, carbon materials, conducting polymers, and their nanocomposites are presented. The sensing material selection, sensor device construction, and sensing mechanism of flexible transparent sensors are discussed in detail. The critical challenges and future development associated with flexible and transparent electronic gas sensors are presented. Smart wearable gas sensors are believed to have great potential in environmental monitoring and noninvasive health monitoring based on disease biomarkers in exhaled gas.

  3. Multi-Gas Sensor

    NASA Technical Reports Server (NTRS)

    Sachse, Glenn W. (Inventor); Wang, Liang-Guo (Inventor); LeBel, Peter J. (Inventor); Steele, Tommy C. (Inventor); Rana, Mauro (Inventor)

    1999-01-01

    A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination element, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band. The difference in intensity between the two orthogonal polarization components is then determined in each partitioned spectral region of interest as an indication of the spectral emission/absorption of the light beam by the gases of interest in the measurement path. The spectral emission/absorption is indicative of the concentration of the one or more gases of interest in the measurement path. More specifically, one embodiment of the present invention is a gas filter correlation radiometer which comprises a polarizer, a polarization modulator, a polarization beam splitter, a beam combiner, wavelength partitioning element, and detection element. The gases of interest are measured simultaneously and, further, can be measured independently or non-independently. Furthermore, optical or electronic element are provided to balance optical intensities between the two optical paths.

  4. New Gas Polarographic Hydrogen Sensor

    NASA Technical Reports Server (NTRS)

    Dominguez, Jesus A.; Barile, Ron

    2004-01-01

    Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor. is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H+ ions or protons; H+ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic 02 sensors are commercially available; a gas polarographic 02 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

  5. Formaldehyde Gas Sensors: A Review

    PubMed Central

    Chung, Po-Ren; Tzeng, Chun-Ta; Ke, Ming-Tsun; Lee, Chia-Yen

    2013-01-01

    Many methods based on spectrophotometric, fluorometric, piezoresistive, amperometric or conductive measurements have been proposed for detecting the concentration of formaldehyde in air. However, conventional formaldehyde measurement systems are bulky and expensive and require the services of highly-trained operators. Accordingly, the emergence of sophisticated technologies in recent years has prompted the development of many microscale gaseous formaldehyde detection systems. Besides their compact size, such devices have many other advantages over their macroscale counterparts, including a real-time response, a more straightforward operation, lower power consumption, and the potential for low-cost batch production. This paper commences by providing a high level overview of the formaldehyde gas sensing field and then describes some of the more significant real-time sensors presented in the literature over the past 10 years or so. PMID:23549368

  6. Electrodes for Semiconductor Gas Sensors.

    PubMed

    Lee, Sung Pil

    2017-03-25

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode-semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode-semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect.

  7. Miniaturized gas ionization sensors using carbon nanotubes.

    PubMed

    Modi, Ashish; Koratkar, Nikhil; Lass, Eric; Wei, Bingqing; Ajayan, Pulickel M

    2003-07-10

    Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

  8. A Rapid Process for Fabricating Gas Sensors

    PubMed Central

    Hsiao, Chun-Ching; Luo, Li-Siang

    2014-01-01

    Zinc oxide (ZnO) is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for “green” usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD) was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (ΔR/R) of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost. PMID:25010696

  9. Handheld chemiresistive gas sensor readout system

    NASA Astrophysics Data System (ADS)

    Joubert, Trudi-Heleen; du Toit, Jurie; Mkwakikunga, Bonex; Bosscha, Peter

    2016-02-01

    Low-cost and non-invasive diabetes diagnosis is increasingly important [1], and this paper presents a handheld readout system for chemiresistive gas sensors in a breath acetone diagnostic application. The sensor contains reference and detection devices, used for the detection of gas concentration. Fabrication is by dropcasting a metaloxide nanowire solution onto gold interdigitated electrodes, which had been manufactured on silicon. The resulting layer is a wide bandgap n-type semiconductor material sensitive to acetone, producing a change in resistance between the electrode terminals [2]. Chemiresistive sensors typically require temperatures of 300-500 °C, while variation of sensing temperature is also employed for selective gas detection. The nano-structured functional material requires low temperatures due to large surface area, but heating is still required for acceptable recovery kinetics. Furthermore, UV illumination improves the sensor recovery [3], and is implemented in this system. Sensor resistances range from 100 Ω to 50 MΩ, while the sensor response time require a sampling frequency of 10Hz. Sensor resistance depends on temperature, humidity, and barometric pressure. The GE CC2A23 temperature sensor is used over a range of -10°C to 60°C, the Honeywell HIH5031 humidity sensor operates up to 85% over this temperature range, and the LPS331AP barometric pressure sensor measures up to 1.25 bar. Honeywell AWM43300V air flow sensors monitor the flow rate up to 1000 sccm. An LCD screen displays all the sensor data, as well as real time date and time, while all measurements are also logged in CSV-format. The system operates from a rechargeable battery.

  10. Porous silicon ammonia gas sensor

    NASA Astrophysics Data System (ADS)

    Chaillou, A.; Charrier, J.; Lorrain, N.; Sarret, M.; Haji, L.

    2006-04-01

    A planar optical waveguide is manufactured by the functionnalisation of oxidised mesoporous silicon with Bromothymol Blue to achieve a sensitive ammonia sensor suitable for low gas concentrations. The propagated light intensity is measured at the output of the waveguide. The sensitivity at low concentrations and the short time of reaction of the sensor are enhanced by a confinement effect of the gas molecules inside the pores. The dependence of the output signal with gas concentration is demonstrated. When the ammonia flow is stopped, the reversibility of the initial characteristics of the propagated light is naturally obtained with the disappearance of the gas molecules.

  11. Sensor array for toxic gas detection

    DOEpatents

    Stetter, Joseph R.; Zaromb, Solomon; Penrose, William R.

    1987-01-01

    A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.

  12. Sub-Nanoliter Spectroscopic Gas Sensor

    PubMed Central

    Alfeeli, Bassam; Pickrell, Gary; Wang, Anbo

    2006-01-01

    In this work, a new type of optical fiber based chemical sensor, the sub-nanoliter sample cell (SNSC) based gas sensor, is described and compared to existing sensors designs in the literature. This novel SNSC gas sensor is shown to have the capability of gas detection with a cell volume in the sub-nanoliter range. Experimental results for various configurations of the sensor design are presented which demonstrate the capabilities of the miniature gas sensor.

  13. Gas sensors based on nanostructured materials.

    PubMed

    Jiménez-Cadena, Giselle; Riu, Jordi; Rius, F Xavier

    2007-11-01

    Gas detection is important for controlling industrial and vehicle emissions, household security and environmental monitoring. In recent decades many devices have been developed for detecting CO(2), CO, SO(2), O(2), O(3), H(2), Ar, N(2), NH(3), H(2)O and several organic vapours. However, the low selectivity or the high operation temperatures required when most gas sensors are used have prompted the study of new materials and the new properties that come about from using traditional materials in a nanostructured mode. In this paper, we have reviewed the main research studies that have been made of gas sensors that use nanomaterials. The main quality characteristics of these new sensing devices have enabled us to make a critical review of the possible advantages and drawbacks of these nanostructured material-based sensors.

  14. Exhaust gas sensors

    SciTech Connect

    Hiller, J.; Miree, T.J.

    1997-02-09

    The automotive industry needed a fast, reliable, under-the-hood method of determining nitrogen oxides in automobile exhaust. Several technologies were pursued concurrently. These sensing technologies were based on light absorption, electrochemical methods, and surface mass loading. The Y-12 plant was selected to study the methods based on light absorption. The first phase was defining the detailed technical objectives of the sensors--this was the role of the automobile companies. The second phase was to develop prototype sensors in the laboratories--the national laboratories. The final phase was testing of the prototype sensors by the automobile industries. This program was canceled a few months into what was to be a three-year effort.

  15. Gas sensor protection device and method

    SciTech Connect

    Boyd, David; Magera, Craig

    2016-11-08

    A gas sensor includes a sensor housing and a sensing element located within the sensor housing. The sensing element has a distal end and defines an axis. The gas sensor also includes a sensor protection device coupled to the sensor housing and at least partially surrounding the distal end of the sensing element. The sensor protection device includes a first member coupled to the housing, the first member having a generally rectangular cross-sectional shape in a plane perpendicular to the axis. The first member includes a gas inlet and a gas outlet. The sensor protection device also includes a second member coupled to the housing.

  16. Development of High Temperature Gas Sensor Technology

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

    1997-01-01

    The measurement of engine emissions is important for their monitoring and control. However, the ability to measure these emissions in-situ is limited. We are developing a family of high temperature gas sensors which are intended to operate in harsh environments such as those in an engine. The development of these sensors is based on progress in two types of technology: (1) The development of SiC-based semiconductor technology; and (2) Improvements in micromachining and microfabrication technology. These technologies are being used to develop point-contact sensors to measure gases which are important in emission control especially hydrogen, hydrocarbons, nitrogen oxides, and oxygen. The purpose of this paper is to discuss the development of this point-contact sensor technology. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. Of particular importance is sensor sensitivity, selectivity, and stability in long-term, high temperature operation. An overview is presented of each sensor type with an evaluation of its stage of development. It is concluded that this technology has significant potential for use in engine applications but further development is necessary.

  17. Black phosphorus gas sensors.

    PubMed

    Abbas, Ahmad N; Liu, Bilu; Chen, Liang; Ma, Yuqiang; Cong, Sen; Aroonyadet, Noppadol; Köpf, Marianne; Nilges, Tom; Zhou, Chongwu

    2015-05-26

    The utilization of black phosphorus and its monolayer (phosphorene) and few-layers in field-effect transistors has attracted a lot of attention to this elemental two-dimensional material. Various studies on optimization of black phosphorus field-effect transistors, PN junctions, photodetectors, and other applications have been demonstrated. Although chemical sensing based on black phosphorus devices was theoretically predicted, there is still no experimental verification of such an important study of this material. In this article, we report on chemical sensing of nitrogen dioxide (NO2) using field-effect transistors based on multilayer black phosphorus. Black phosphorus sensors exhibited increased conduction upon NO2 exposure and excellent sensitivity for detection of NO2 down to 5 ppb. Moreover, when the multilayer black phosphorus field-effect transistor was exposed to NO2 concentrations of 5, 10, 20, and 40 ppb, its relative conduction change followed the Langmuir isotherm for molecules adsorbed on a surface. Additionally, on the basis of an exponential conductance change, the rate constants for adsorption and desorption of NO2 on black phosphorus were extracted for different NO2 concentrations, and they were in the range of 130-840 s. These results shed light on important electronic and sensing characteristics of black phosphorus, which can be utilized in future studies and applications.

  18. Oxygen sensor for monitoring gas mixtures containing hydrocarbons

    DOEpatents

    Ruka, R.J.; Basel, R.A.

    1996-03-12

    A gas sensor measures O{sub 2} content of a reformable monitored gas containing hydrocarbons, H{sub 2}O and/or CO{sub 2}, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system. 4 figs.

  19. Oxygen sensor for monitoring gas mixtures containing hydrocarbons

    DOEpatents

    Ruka, Roswell J.; Basel, Richard A.

    1996-01-01

    A gas sensor measures O.sub.2 content of a reformable monitored gas containing hydrocarbons H.sub.2 O and/or CO.sub.2, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system.

  20. Bimodular high temperature planar oxygen gas sensor

    PubMed Central

    Sun, Xiangcheng; Liu, Yixin; Gao, Haiyong; Gao, Pu-Xian; Lei, Yu

    2014-01-01

    A bimodular planar O2 sensor was fabricated using NiO nanoparticles (NPs) thin film coated yttria-stabilized zirconia (YSZ) substrate. The thin film was prepared by radio frequency (r.f.) magnetron sputtering of NiO on YSZ substrate, followed by high temperature sintering. The surface morphology of NiO NPs film was characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). X-ray diffraction (XRD) patterns of NiO NPs thin film before and after high temperature O2 sensing demonstrated that the sensing material possesses a good chemical and structure stability. The oxygen detection experiments were performed at 500, 600, and 800°C using the as-prepared bimodular O2 sensor under both potentiometric and resistance modules. For the potentiometric module, a linear relationship between electromotive force (EMF) output of the sensor and the logarithm of O2 concentration was observed at each operating temperature, following the Nernst law. For the resistance module, the logarithm of electrical conductivity was proportional to the logarithm of oxygen concentration at each operating temperature, in good agreement with literature report. In addition, this bimodular sensor shows sensitive, reproducible and reversible response to oxygen under both sensing modules. Integration of two sensing modules into one sensor could greatly enrich the information output and would open a new venue in the development of high temperature gas sensors. PMID:25191652

  1. Combustion Sensors: Gas Turbine Applications

    NASA Technical Reports Server (NTRS)

    Human, Mel

    2002-01-01

    This report documents efforts to survey the current research directions in sensor technology for gas turbine systems. The work is driven by the current and future requirements on system performance and optimization. Accurate real time measurements of velocities, pressure, temperatures, and species concentrations will be required for objectives such as combustion instability attenuation, pollutant reduction, engine health management, exhaust profile control via active control, etc. Changing combustor conditions - engine aging, flow path slagging, or rapid maneuvering - will require adaptive responses; the effectiveness of such will be only as good as the dynamic information available for processing. All of these issues point toward the importance of continued sensor development. For adequate control of the combustion process, sensor data must include information about the above mentioned quantities along with equivalence ratios and radical concentrations, and also include both temporal and spatial velocity resolution. Ultimately these devices must transfer from the laboratory to field installations, and thus must become low weight and cost, reliable and maintainable. A primary conclusion from this study is that the optics-based sensor science will be the primary diagnostic in future gas turbine technologies.

  2. Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zan, Hsiao-Wen; Li, Chang-Hung; Yeh, Chun-Cheng; Dai, Ming-Zhi; Meng, Hsin-Fei; Tsai, Chuang-Chuang

    2011-06-01

    An organic sensing layer is capped onto an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction with the a-IGZO film. Oxidizing or reducing vapor molecules act like electron acceptors or electron donors to change the potential of the organic layer and the current of a-IGZO TFT. A sensitive and reversible response to 100 ppb ammonia and 100 ppb acetone is obtained at room temperature. This letter opens a route to develop low-cost large-area bio/chemical sensor arrays based on the emerging a-IGZO TFT technology.

  3. Gas Sensors Based on Conducting Polymers

    PubMed Central

    Bai, Hua; Shi, Gaoquan

    2007-01-01

    The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

  4. Carbon-Nanotube-Based Chemical Gas Sensor

    NASA Technical Reports Server (NTRS)

    Kaul, Arunpama B.

    2010-01-01

    Conventional thermal conductivity gauges (e.g. Pirani gauges) lend themselves to applications such as leak detectors, or in gas chromatographs for identifying various gas species. However, these conventional gauges are physically large, operate at high power, and have a slow response time. A single-walled carbon-nanotube (SWNT)-based chemical sensing gauge relies on differences in thermal conductance of the respective gases surrounding the CNT as it is voltage-biased, as a means for chemical identification. Such a sensor provides benefits of significantly reduced size and compactness, fast response time, low-power operation, and inexpensive manufacturing since it can be batch-fabricated using Si integrated-circuit (IC) process technology.

  5. Ultrafast response sensor to formaldehyde gas based on metal oxide.

    PubMed

    Choi, N-J; Lee, H-K; Moon, S E; Kim, J; Yang, W S

    2014-08-01

    Thick film semiconductor gas sensors based on indium oxide were fabricated on Si substrate. The sensing materials on Si substrate were characterized using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and so on. They were very fine and uniform and we found out that particle sizes were about 20~30 nm through XRD analysis. Gas responses of fabricated sensors were measured in a chamber where gas flow was controlled by mass flow controller (MFC). Their resistance changes were monitored in real time by using data acquisition board and personal computer. Gas response characteristics were examined for formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. Particularly, the sensors showed responses to formaldehyde gas at sub ppm (cf, standard of natural environment in building is about 80 ppb by ministry of environment in Korea), as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repetition, selectivity, response speed and reproducibility of the sensors. The lowest detection limit is HCHO 25 ppb and sensitivity at 800 ppb is over 25% at 350 °C operating temperature. The response time (8 s) and recovery time (15 s) to HCHO gas at 200 ppb were very fast compared to other commercial products in flow type measurement condition. Repetition measurement was very good with ±3% in full measurement range. The fabricated metal oxide gas sensor showed good performance to HCHO gas and proved that it could be adaptable to indoor environment in building.

  6. Mocvd of Tin Oxide for Gas Sensors.

    NASA Astrophysics Data System (ADS)

    Weglicki, Peter Stanislaw

    1990-01-01

    Available from UMI in association with The British Library. Requires signed TDF. Thin films of a wide variety of materials can be produced using an assortment of physical and chemical techniques. Such techniques are reviewed and compared, with particular reference to the deposition of tin oxide films. In the present study, MOCVD (Metal organic chemical vapour deposition) was used to grow thin films of tin oxide from dibutyltin diacetate precursor on a variety of substrates. A series of reactor prototypes were developed in accordance with specific requirements of reproducibility and process control. The evolution of the designs leading to the final working system is detailed. The theory of MOCVD is given with particular reference to the reactor used in this project. The effects of various deposition parameters on tin oxide film growth rates were investigated, and the results are discussed with reference to the deposition kinetics in the system. Films were characterised by optical interferometry, optical and electron microscopy, X-ray diffraction, Rutherford backscattering and electrical measurements. The films were generally uniform, conducting and polycrystalline, and were comprised of very small grains, resulting in a high density. A specific application of metal oxide materials is in solid state gas sensors, which are available in various forms and operate according to different mechanisms. These are compared and a detailed account is given on the theory of operation of surface conductivity modulated devices. The application of such devices based on tin oxide in thin film form was investigated in the present work. The prepared sensor samples were comprised of very small grains, resulting in a high density. The observation that preferred (310) orientation occured in thicker films, can be attributed to dendritic growth. The sensors generally showed response to numerous reducing gas ambients, although there was evidence of a degree of selectivity against methane

  7. Ammonia gas sensors based on In2O3/PANI hetero-nanofibers operating at room temperature.

    PubMed

    Nie, Qingxin; Pang, Zengyuan; Lu, Hangyi; Cai, Yibing; Wei, Qufu

    2016-01-01

    Indium nitrate/polyvinyl pyrrolidone (In(NO3)3/PVP) composite nanofibers were synthesized via electrospinning, and then hollow structure indium oxide (In2O3) nanofibers were obtained through calcination with PVP as template material. In situ polymerization was used to prepare indium oxide/polyaniline (In2O3/PANI) composite nanofibers with different mass ratios of In2O3 to aniline. The structure and morphology of In(NO3)3/PVP, In2O3/PANI composite nanofibers and pure PANI were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and current-voltage (I-V) measurements. The gas sensing properties of these materials towards NH3 vapor (100 to 1000 ppm) were measured at room temperature. The results revealed that the gas sensing abilities of In2O3/PANI composite nanofibers were better than pure PANI. In addition, the mass ratio of In2O3 to aniline and the p-n heterostructure between In2O3 and PANI influences the sensing performance of the In2O3/PANI composite nanofibers. In this paper, In2O3/PANI composite nanofibers with a mass ratio of 1:2 exhibited the highest response values, excellent selectivity, good repeatability and reversibility.

  8. Ammonia gas sensors based on In2O3/PANI hetero-nanofibers operating at room temperature

    PubMed Central

    Nie, Qingxin; Pang, Zengyuan; Lu, Hangyi; Cai, Yibing

    2016-01-01

    Summary Indium nitrate/polyvinyl pyrrolidone (In(NO3)3/PVP) composite nanofibers were synthesized via electrospinning, and then hollow structure indium oxide (In2O3) nanofibers were obtained through calcination with PVP as template material. In situ polymerization was used to prepare indium oxide/polyaniline (In2O3/PANI) composite nanofibers with different mass ratios of In2O3 to aniline. The structure and morphology of In(NO3)3/PVP, In2O3/PANI composite nanofibers and pure PANI were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and current–voltage (I–V) measurements. The gas sensing properties of these materials towards NH3 vapor (100 to 1000 ppm) were measured at room temperature. The results revealed that the gas sensing abilities of In2O3/PANI composite nanofibers were better than pure PANI. In addition, the mass ratio of In2O3 to aniline and the p–n heterostructure between In2O3 and PANI influences the sensing performance of the In2O3/PANI composite nanofibers. In this paper, In2O3/PANI composite nanofibers with a mass ratio of 1:2 exhibited the highest response values, excellent selectivity, good repeatability and reversibility. PMID:27826505

  9. Sensor-Web Operations Explorer

    NASA Technical Reports Server (NTRS)

    Meemong, Lee; Miller, Charles; Bowman, Kevin; Weidner, Richard

    2008-01-01

    Understanding the atmospheric state and its impact on air quality requires observations of trace gases, aerosols, clouds, and physical parameters across temporal and spatial scales that range from minutes to days and from meters to more than 10,000 kilometers. Observations include continuous local monitoring for particle formation; field campaigns for emissions, local transport, and chemistry; and periodic global measurements for continental transport and chemistry. Understanding includes global data assimilation framework capable of hierarchical coupling, dynamic integration of chemical data and atmospheric models, and feedback loops between models and observations. The objective of the sensor-web system is to observe trace gases, aerosols, clouds, and physical parameters, an integrated observation infrastructure composed of space-borne, air-borne, and in-situ sensors will be simulated based on their measurement physics properties. The objective of the sensor-web operation is to optimally plan for heterogeneous multiple sensors, the sampling strategies will be explored and science impact will be analyzed based on comprehensive modeling of atmospheric phenomena including convection, transport, and chemical process. Topics include system architecture, software architecture, hardware architecture, process flow, technology infusion, challenges, and future direction.

  10. Nano-Hydroxyapatite Thick Film Gas Sensors

    SciTech Connect

    Khairnar, Rajendra S.; Mene, Ravindra U.; Munde, Shivaji G.; Mahabole, Megha P.

    2011-12-10

    In the present work pure and metal ions (Co and Fe) doped hydroxyapatite (HAp) thick films have been successfully utilized to improve the structural, morphological and gas sensing properties. Nanocrystalline HAp powder is synthesized by wet chemical precipitation route, and ion exchange process is employed for addition of Co and Fe ions in HAp matrix. Moreover, swift heavy ion irradiation (SHI) technique is used to modify the surface of pure and metal ion exchanged HAp with various ion fluence. The structural investigation of pure and metal ion exchanged HAp thick films are carried out using X-ray diffraction and the presence of functional group is observed by means FTIR spectroscopy. Furthermore, surface morphology is visualized by means of SEM and AFM analysis. CO gas sensing study is carried out for, pure and metal ions doped, HAp thick films with detail investigation on operating temperature, response/recovery time and gas uptake capacity. The surface modifications of sensor matrix by SHI enhance the gas response, response/recovery and gas uptake capacity. The significant observation is here to note that, addition of Co and Fe in HAp matrix and surface modification by SHI improves the sensing properties of HAp films drastically resulting in gas sensing at relatively lower temperatures.

  11. Optical fiber gas sensor development and application

    NASA Astrophysics Data System (ADS)

    Jin, W.; Ho, H. L.

    2008-12-01

    This paper reports recent development and application of optical fiber gas sensors using absorption spectroscopy, including open-path gas sensors using fiber coupled micro-optic cells and photonic bandgap (PBG) fibers. A fiber-optic sensor system capable of detecting dissolved fault gases in oil-insulated equipment in power industry is presented. The gases include methane (CH4), acetylene (C2H2) and ethylene (C2H4). In addition, the development of gas sensor using PBG fiber will be reported.

  12. Development of Sic Gas Sensor Systems

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Okojie, R. S.; Beheim, G. M.; Thomas, V.; Chen, L.; Lukco, D.; Liu, C. C.; Ward, B.; Makel, D.

    2002-01-01

    Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable enabling technologies to make a complete gas sensor system: electrical contacts, packaging, and transfer of information from the sensor to the outside world. This paper reviews the status at NASA Glenn Research Center of SiC Schottky diode gas sensor development as well as that of enabling technologies supporting SiC gas sensor system implementation. A vision of a complete high temperature microfabricated SiC gas sensor system is proposed. In the long-term, it is believed that improvements in the SiC semiconductor material itself could have a dramatic effect on the performance of SiC gas sensor systems.

  13. A Large Scale Virtual Gas Sensor Array

    NASA Astrophysics Data System (ADS)

    Ziyatdinov, Andrey; Fernández-Diaz, Eduard; Chaudry, A.; Marco, Santiago; Persaud, Krishna; Perera, Alexandre

    2011-09-01

    This paper depicts a virtual sensor array that allows the user to generate gas sensor synthetic data while controlling a wide variety of the characteristics of the sensor array response: arbitrary number of sensors, support for multi-component gas mixtures and full control of the noise in the system such as sensor drift or sensor aging. The artificial sensor array response is inspired on the response of 17 polymeric sensors for three analytes during 7 month. The main trends in the synthetic gas sensor array, such as sensitivity, diversity, drift and sensor noise, are user controlled. Sensor sensitivity is modeled by an optionally linear or nonlinear method (spline based). The toolbox on data generation is implemented in open source R language for statistical computing and can be freely accessed as an educational resource or benchmarking reference. The software package permits the design of scenarios with a very large number of sensors (over 10000 sensels), which are employed in the test and benchmarking of neuromorphic models in the Bio-ICT European project NEUROCHEM.

  14. NOVEL GAS SENSORS FOR HIGH-TEMPERATURE FOSSIL FUEL APPLICATIONS

    SciTech Connect

    Palitha Jayaweera

    2004-05-01

    SRI is developing ceramic-based microsensors for detection of exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes and are designed to operate at high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. Under this research project we are developing sensors for multiple gas detection in a single package along with data acquisition and control software and hardware. The sensor package can be easily integrated into online monitoring systems for active emission control. This report details the research activities performed from October 2003 to April 2004.

  15. Silicon Carbide Gas Sensors for Propulsion Emissions and Safety Applications

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Xu, J.; Neudeck, P. G.; Lukco, D.; Trunek, A.; Spry, D.; Lampard, P.; Androjna, D.; Makel, D.; Ward, B.

    2007-01-01

    Silicon carbide (SiC) based gas sensors have the ability to meet the needs of a range of aerospace propulsion applications including emissions monitoring, leak detection, and hydrazine monitoring. These applications often require sensitive gas detection in a range of environments. An effective sensing approach to meet the needs of these applications is a Schottky diode based on a SiC semiconductor. The primary advantage of using SiC as a semiconductor is its inherent stability and capability to operate at a wide range of temperatures. The complete SiC Schottky diode gas sensing structure includes both the SiC semiconductor and gas sensitive thin film metal layers; reliable operation of the SiC-based gas sensing structure requires good control of the interface between these gas sensitive layers and the SiC. This paper reports on the development of SiC gas sensors. The focus is on two efforts to better control the SiC gas sensitive Schottky diode interface. First, the use of palladium oxide (PdOx) as a barrier layer between the metal and SiC is discussed. Second, the use of atomically flat SiC to provide an improved SiC semiconductor surface for gas sensor element deposition is explored. The use of SiC gas sensors in a multi-parameter detection system is briefly discussed. It is concluded that SiC gas sensors have potential in a range of propulsion system applications, but tailoring of the sensor for each application is necessary.

  16. Platform for a Hydrocarbon Exhaust Gas Sensor Utilizing a Pumping Cell and a Conductometric Sensor

    PubMed Central

    Biskupski, Diana; Geupel, Andrea; Wiesner, Kerstin; Fleischer, Maximilian; Moos, Ralf

    2009-01-01

    Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well. PMID:22423212

  17. Porous Silicon Structures as Optical Gas Sensors

    PubMed Central

    Levitsky, Igor A.

    2015-01-01

    We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi) and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers) are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed. PMID:26287199

  18. SiC-Based Gas Sensor Development

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Gray, M.; Androjna, D.; Chen, L.-Y.; Hoffman, R. W., Jr.; Liu, C. C.; Wu, Q. H.

    2000-01-01

    Silicon carbide based Schottky diode gas sensors are being developed for applications such as emission measurements and leak detection. The effects of the geometry of the tin oxide film in a Pd/SnO2/SiC structure will be discussed as well as improvements in packaging SiC-based sensors. It is concluded that there is considerable versatility in the formation of SiC-based Schottky diode gas sensing structures which will potentially allow the fabrication of a SiC-based gas sensor array for a variety of gases and temperatures.

  19. Multiple frequency method for operating electrochemical sensors

    DOEpatents

    Martin, Louis P [San Ramon, CA

    2012-05-15

    A multiple frequency method for the operation of a sensor to measure a parameter of interest using calibration information including the steps of exciting the sensor at a first frequency providing a first sensor response, exciting the sensor at a second frequency providing a second sensor response, using the second sensor response at the second frequency and the calibration information to produce a calculated concentration of the interfering parameters, using the first sensor response at the first frequency, the calculated concentration of the interfering parameters, and the calibration information to measure the parameter of interest.

  20. Infrared hyperspectral imaging sensor for gas detection

    NASA Astrophysics Data System (ADS)

    Hinnrichs, Michele

    2000-11-01

    A small light weight man portable imaging spectrometer has many applications; gas leak detection, flare analysis, threat warning, chemical agent detection, just to name a few. With support from the US Air Force and Navy, Pacific Advanced Technology has developed a small man portable hyperspectral imaging sensor with an embedded DSP processor for real time processing that is capable of remotely imaging various targets such as gas plums, flames and camouflaged targets. Based upon their spectral signature the species and concentration of gases can be determined. This system has been field tested at numerous places including White Mountain, CA, Edwards AFB, and Vandenberg AFB. Recently evaluation of the system for gas detection has been performed. This paper presents these results. The system uses a conventional infrared camera fitted with a diffractive optic that images as well as disperses the incident radiation to form spectral images that are collected in band sequential mode. Because the diffractive optic performs both imaging and spectral filtering, the lens system consists of only a single element that is small, light weight and robust, thus allowing man portability. The number of spectral bands are programmable such that only those bands of interest need to be collected. The system is entirely passive, therefore, easily used in a covert operation. Currently Pacific Advanced Technology is working on the next generation of this camera system that will have both an embedded processor as well as an embedded digital signal processor in a small hand held camera configuration. This will allow the implementation of signal and image processing algorithms for gas detection and identification in real time. This paper presents field test data on gas detection and identification as well as discuss the signal and image processing used to enhance the gas visibility. Flow rates as low as 0.01 cubic feet per minute have been imaged with this system.

  1. a Novel Method for Gas Sensors Characterization

    NASA Astrophysics Data System (ADS)

    Mielle, P.; Marquis, F.; Trivier, V.

    2000-12-01

    For E-nose applications, sensors are never specified towards the aroma chemicals, because it is difficult to generate a known amount of chemical vapours from a condensed phase. A method was developed, that allows the specification of gas sensors towards food samples, using a GC/sensors coupling. We have found the ADL lower than the GC-FID detector, and an unexpected response for E.V. Olive Oil.

  2. Hydrogen gas sensor and method of manufacture

    DOEpatents

    McKee, John M.

    1991-01-01

    A sensor for measuring the pressure of hydrogen gas in a nuclear reactor, and method of manufacturing the same. The sensor comprises an elongated tube of hydrogen permeable material which is connected to a pressure transducer through a feedthrough tube which passes through a wall at the boundary of the region in which hydrogen is present. The tube is pressurized and flushed with hydrogen gas at an elevated temperature during the manufacture of the sensor in order to remove all gasses other than hydrogen from the device.

  3. Integrated Microfluidic Gas Sensors for Water Monitoring

    NASA Technical Reports Server (NTRS)

    Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

    2003-01-01

    A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

  4. Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior

    PubMed Central

    Cui, Ling; Murray, Erica P.

    2015-01-01

    The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sensors was collected via impedance spectroscopy under various operating conditions where gas concentrations ranged from 0 to 100 ppm NO and 1%–18% O2 at temperatures varying from 600 to 700 °C. Gas diffusion appeared to be a rate-limiting mechanism in sensors where the electrode configuration resulted in longer diffusion pathways. The temperature dependence of the NO sensors studied was independent of the electrode configuration. Analysis of the impedance data, along with equivalent circuit modeling indicated the electrode configuration of the sensor effected gas and ionic transport pathways, capacitance behavior, and NO sensitivity. PMID:26404312

  5. Electrochemical amperometric gas sensors for environmental monitoring and control

    NASA Technical Reports Server (NTRS)

    Venkatasetty, H. V.

    1990-01-01

    Theoretical considerations and experimental results regarding a unique class of vapor sensors are presented, and the sensors are compared to semiconductor-based sensors. The electrochemical sensors are based on nonaquaeous electrolytes, and gas-detection selectivity achieved by applying a known potential to the sensing electrode using a reference electrode and a counter electrode. Results are given regarding the detection of oxygen and carbon dioxide using one cell, the detection of 3-percent carbon dioxide in nitrogen, and the detection of carbon dioxide in air at percentages ranging from 3 to 6. The sensors are found to be effective in the detection of toxic chemical species including CO, NO2, and formaldehyde; the sensors are further found to require minimal power, operate over long periods of time, and function over a wide temperature range.

  6. Gas Sensors Based on Electrospun Nanofibers

    PubMed Central

    Ding, Bin; Wang, Moran; Yu, Jianyong; Sun, Gang

    2009-01-01

    Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films. PMID:22573976

  7. Polypyrrole based gas sensor for ammonia detection

    NASA Astrophysics Data System (ADS)

    Dunst, K. J.; Cysewska, K.; Kalinowski, P.; Jasiński, P.

    2016-01-01

    The nature of polypyrrole response to toxic gases does not allow using the sensor in a conventional way. The main aim of this study is to acquire the information about the concentration using different approaches: a linear approximation, a non-linear approximation and a tangent method. In this paper a two-steps procedure for sensor response measurements has been utilized. Polypyrrole films were electrochemically synthesized on the interdigitated electrodes. Gas sensing measurements of polypyrrole based sensor were carried out at room temperature. The influence of the flow rate on the sensing performance to NH3 were investigated. The preliminary studies of aging of the sensor were also explored.

  8. Nanostructured Materials for Room-Temperature Gas Sensors.

    PubMed

    Zhang, Jun; Liu, Xianghong; Neri, Giovanni; Pinna, Nicola

    2016-02-03

    Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high-performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high-temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room-temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room-temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure-property correlations. Finally, some future research perspectives and new challenges that the field of room-temperature sensors will have to address are also discussed.

  9. Biomaterial based sulphur di oxide gas sensor

    NASA Astrophysics Data System (ADS)

    Ghosh, P. K.; Sarkar, A.

    2013-06-01

    Biomaterials are getting importance in the present research field of sensors. In this present paper performance of biomaterial based gas sensor made of gum Arabica and garlic extract had been studied. Extract of garlic clove with multiple medicinal and chemical utility can be proved to be useful in sensing Sulphur di Oxide gas. On exposure to Sulphur di Oxide gas the material under observation suffers some temporary structural change, which can be observed in form of amplified potentiometric change through simple electronic circuitry. Exploiting this very property a potentiometric gas sensor of faster response and recovery time can be designed. In this work sensing property of the said material has been studied through DC conductance, FTIR spectrum etc.

  10. Graphene Based Flexible Gas Sensors

    NASA Astrophysics Data System (ADS)

    Yi, Congwen

    Graphene is a novel carbon material with great promise for a range of applications due to its electronic and mechanical properties. Its two-dimensional nature translates to a high sensitivity to surface chemical interactions thereby making it an ideal platform for sensors. Graphene's electronic properties are not degraded due to mechanical flexing or strain (Kim, K. S., et al. nature 07719, 2009) offering another advantage for flexible sensors integrated into numerous systems including fabrics, etc. We have demonstrated a graphene NO2 sensor on a solid substrate (100nm SiO2/heavily doped silicon). Three different methods were used to synthesize graphene and the sensor fabrication process was optimized accordingly. Water is used as a controllable p-type dopant in graphene to study the relationship between doping and graphene's response to NO2 . Experimental results show that interface water between graphene and the supporting SiO2 substrate induces higher p-doping in graphene, leading to a higher sensitivity to NO2, consistent with theoretical predications (Zhang, Y. et al., Nanotechnology 20(2009) 185504). We have also demonstrated a flexible and stretchable graphene-based sensor. Few layer graphene, grown on a Ni substrate, is etched and transferred to a highly stretchable polymer substrate (VHB from 3M) with preloaded stress, followed by metal contact formation to construct a flexible, stretchable sensor. With up to 500% deformation caused by compressive stress, graphene still shows stable electrical response to NO2. Our results suggest that higher compressive stress results in smaller sheet resistance and higher sensitivity to NO2. A possible molecular detection sensor utilizing Surface Enhanced Raman Spectrum (SERS) based on a graphene/gallium nanoparticles platform is also studied. By correlating the enhancement of the graphene Raman modes with metal coverage, we propose that the Ga transfers electrons to the graphene creating local regions of enhanced

  11. Development of a hydrogen gas sensor using microfabrication technology

    NASA Technical Reports Server (NTRS)

    Liu, Chung-Chiun; Wu, Qinghai; Stuczynski, Matthew; Madzsar, George C.

    1992-01-01

    Microfabrication and micromachining technologies are used to produce a hydrogen gas sensor based on a palladium-silver film. The sensor uses a heater that is fabricated by diffusing p-type borones into the substrate, forming a resistance heater. A diode for temperature measurement is produced using p-type boron and n-type phosphor diffused into the substrate. A thickness of the palladium-silver film is approximately 300 arcsec. The hydrogen gas sensor employs the proven palladium-silver diode structure and is surrounded by a phosphor doped resistance heater which can be heated up to a temperature of 250 C. Experimental results show that the sensor is capable of operating over a wide range of hydrogen concentration levels between 0-95 percent without any hysteresis effects.

  12. NOVEL GAS SENSORS FOR HIGH-TEMPERATURE FOSSIL FUEL APPLICATIONS

    SciTech Connect

    Palitha Jayaweera

    2004-05-01

    SRI is developing ceramic-based microsensors for detection of exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes and are designed to operate at high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. Under this research project we are developing sensors for multiple gas detection in a single package along with data acquisition and control software and hardware. The sensor package can be easily integrated into online monitoring systems for active emission control. This report details the research activities performed from May 2004 to October 2004 including testing of catalytic materials, sensor design and fabrication, and software development.

  13. Sensor validation and fusion for gas turbine vibration monitoring

    NASA Astrophysics Data System (ADS)

    Yan, Weizhong; Goebel, Kai F.

    2003-08-01

    Vibration monitoring is an important practice throughout regular operation of gas turbine power systems and, even more so, during characterization tests. Vibration monitoring relies on accurate and reliable sensor readings. To obtain accurate readings, sensors are placed such that the signal is maximized. In the case of characterization tests, strain gauges are placed at the location of vibration modes on blades inside the gas turbine. Due to the prevailing harsh environment, these sensors have a limited life and decaying accuracy, both of which impair vibration assessment. At the same time bandwidth limitations may restrict data transmission, which in turn limits the number of sensors that can be used for assessment. Knowing the sensor status (normal or faulty), and more importantly, knowing the true vibration level of the system all the time is essential for successful gas turbine vibration monitoring. This paper investigates a dynamic sensor validation and system health reasoning scheme that addresses the issues outlined above by considering only the information required to reliably assess system health status. In particular, if abnormal system health is suspected or if the primary sensor is determined to be faulted, information from available "sibling" sensors is dynamically integrated. A confidence expresses the complex interactions of sensor health and system health, their reliabilities, conflicting information, and what the health assessment is. Effectiveness of the scheme in achieving accurate and reliable vibration evaluation is then demonstrated using a combination of simulated data and a small sample of a real-world application data where the vibration of compressor blades during a real time characterization test of a new gas turbine power system is monitored.

  14. High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.

    2002-01-01

    The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for

  15. Towards Enhanced Gas Sensor Performance with Fluoropolymer Membranes

    PubMed Central

    Graunke, Thorsten; Schmitt, Katrin; Raible, Stefan; Wöllenstein, Jürgen

    2016-01-01

    In this paper we report on how to increase the selectivity of gas sensors by using fluoropolymer membranes. The mass transport of polar and non-polar gases through a polymer membrane matrix was studied by systematic selection of polymers with different degrees of fluorination, as well as polymers whose monomers have ether groups (-O-) in addition to fluorine groups (-F). For the study, a set of application-relevant gases including H2, CO, CO2, NO2, methane, ethanol, acetone, and acetaldehyde as well as various concentrations of relative humidity were used. These gases have different functional groups and polarities, yet have a similar kinetic diameter and are therefore typically difficult to separate. The concentrations of the gases were chosen according to international indicative limit values (TWA, STEL). To measure the concentration in the feed and permeate, we used tin-dioxide-based metal oxide gas sensors with palladium catalyst (SnO2:Pd), catalytic sensors (also SnO2:Pd-based) and thermal conductivity sensors. This allows a close examination of the interdependence of diffusion and physicochemical operating principle of the sensor. Our goal is to increase the selectivity of gas sensors by using inexpensive fluoropolymer membranes. The measurements showed that through membranes with low polarity, preferably non-polar gases are transported. Furthermore, the degree of crystallization influences the permeability and selectivity of a polymer membrane. Basically the polar polymers showed a higher permeability to water vapor and polar substances than non-polar polymer membranes. PMID:27690045

  16. Miniaturization of a biomedical gas sensor.

    PubMed

    Mirtaheri, Peyman; Omtveit, Tore; Klotzbuecher, Thomas; Grimnes, Sverre; Martinsen, Orjan G; Tønnessen, Tor Inge

    2004-12-01

    In a previous study, we concluded that a conductivity based PCO2 sensor is an attractive solution for early detection of ischemia and presented two design geometries. For organ surface measurements, the planar design was suitable but it was difficult to insert the sensor into the tissue. A cylindrical design solution was favored for insertion due to the large membrane contact area and easy placement in a medical catheter. Since the previous cylindrical prototype was large and could damage the tissue, a more miniaturized sensor was needed. In the current paper, we present a miniaturized sensor with an outer diameter of 1 mm. The applied technology for manufacturing the sensor was a combination of mechanical turning, excimer laser drilling and conventional molding technique. The materials applied were PEEK (polyetherether ketone), PI (polyimide) with gold layers and polysiloxane. The membrane had to be gas permeable while acting as a barrier for ion transport, and was made of polysiloxane and had a thickness of 100-150 microm. The miniaturized sensor was tested for calibration, response time, drifting and pressure sensitivity. The results show that the miniaturized PCO2 sensor is capable of rapid and stable measurements both in vitro and ex vivo. The result from this study will be applied for the industrial manufacturing of such a biomedical sensor as a clinical product.

  17. A low-temperature ZnO nanowire ethanol gas sensor prepared on plastic substrate

    NASA Astrophysics Data System (ADS)

    Lin, Chih-Hung; Chang, Shoou-Jinn; Hsueh, Ting-Jen

    2016-09-01

    In this work, a low-temperature ZnO nanowire ethanol gas sensor was prepared on plastic substrate. The operating temperature of the ZnO nanowire ethanol gas sensor was reduced to room temperature using ultraviolet illumination. The experimental results indicate a favorable sensor response at low temperature, with the best response at 60 °C. The results also reveal that the ZnO nanowire ethanol gas sensor can be easily integrated into portable products, whose waste heat can improve sensor response and achieve energy savings, while energy consumption can be further reduced by solar irradiation.

  18. Acetone Sensing Properties of a Gas Sensor Composed of Carbon Nanotubes Doped With Iron Oxide Nanopowder

    PubMed Central

    Tan, Qiulin; Fang, Jiahua; Liu, Wenyi; Xiong, Jijun; Zhang, Wendong

    2015-01-01

    Iron oxide (Fe2O3) nanopowder was prepared by a precipitation method and then mixed with different proportions of carbon nanotubes. The composite materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. A fabricated heater-type gas sensor was compared with a pure Fe2O3 gas sensor under the influence of acetone. The effects of the amount of doping, the sintering temperature, and the operating temperature on the response of the sensor and the response recovery time were analyzed. Experiments show that doping of carbon nanotubes with iron oxide effectively improves the response of the resulting gas sensors to acetone gas. It also reduces the operating temperature and shortens the response recovery time of the sensor. The response of the sensor in an acetone gas concentration of 80 ppm was enhanced, with good repeatability. PMID:26569253

  19. Self-Activated Transparent All-Graphene Gas Sensor with Endurance to Humidity and Mechanical Bending.

    PubMed

    Kim, Yeon Hoo; Kim, Sang Jin; Kim, Yong-Jin; Shim, Yeong-Seok; Kim, Soo Young; Hong, Byung Hee; Jang, Ho Won

    2015-10-27

    Graphene is considered as one of leading candidates for gas sensor applications in the Internet of Things owing to its unique properties such as high sensitivity to gas adsorption, transparency, and flexibility. We present self-activated operation of all graphene gas sensors with high transparency and flexibility. The all-graphene gas sensors which consist of graphene for both sensor electrodes and active sensing area exhibit highly sensitive, selective, and reversible responses to NO2 without external heating. The sensors show reliable operation under high humidity conditions and bending strain. In addition to these remarkable device performances, the significantly facile fabrication process enlarges the potential of the all-graphene gas sensors for use in the Internet of Things and wearable electronics.

  20. Sensor study for high speed autonomous operations

    NASA Astrophysics Data System (ADS)

    Schneider, Anne; La Celle, Zachary; Lacaze, Alberto; Murphy, Karl; Del Giorno, Mark; Close, Ryan

    2015-06-01

    As robotic ground systems advance in capabilities and begin to fulfill new roles in both civilian and military life, the limitation of slow operational speed has become a hindrance to the wide-spread adoption of these systems. For example, military convoys are reluctant to employ autonomous vehicles when these systems slow their movement from 60 miles per hour down to 40. However, these autonomous systems must operate at these lower speeds due to the limitations of the sensors they employ. Robotic Research, with its extensive experience in ground autonomy and associated problems therein, in conjunction with CERDEC/Night Vision and Electronic Sensors Directorate (NVESD), has performed a study to specify system and detection requirements; determined how current autonomy sensors perform in various scenarios; and analyzed how sensors should be employed to increase operational speeds of ground vehicles. The sensors evaluated in this study include the state of the art in LADAR/LIDAR, Radar, Electro-Optical, and Infrared sensors, and have been analyzed at high speeds to study their effectiveness in detecting and accounting for obstacles and other perception challenges. By creating a common set of testing benchmarks, and by testing in a wide range of real-world conditions, Robotic Research has evaluated where sensors can be successfully employed today; where sensors fall short; and which technologies should be examined and developed further. This study is the first step to achieve the overarching goal of doubling ground vehicle speeds on any given terrain.

  1. A wafer-level liquid cavity integrated amperometric gas sensor with ppb-level nitric oxide gas sensitivity

    NASA Astrophysics Data System (ADS)

    Gatty, Hithesh K.; Stemme, Göran; Roxhed, Niclas

    2015-10-01

    A miniaturized amperometric nitric oxide (NO) gas sensor based on wafer-level fabrication of electrodes and a liquid electrolyte chamber is reported in this paper. The sensor is able to detect NO gas concentrations of the order of parts per billion (ppb) levels and has a measured sensitivity of 0.04 nA ppb-1 with a response time of approximately 12 s. A sufficiently high selectivity of the sensor to interfering gases such as carbon monoxide (CO) and to ammonia (NH3) makes it potentially relevant for monitoring of asthma. In addition, the sensor was characterized for electrolyte evaporation which indicated a sensor operation lifetime allowing approximately 200 measurements.

  2. Construction of a Polyaniline Nanofiber Gas Sensor

    ERIC Educational Resources Information Center

    Virji, Shabnam; Weiller, Bruce H.; Huang, Jiaxing; Blair, Richard; Shepherd, Heather; Faltens, Tanya; Haussmann, Philip C.; Kaner, Richard B.; Tolbert, Sarah H.

    2008-01-01

    The electrical properties of polyaniline changes by orders of magnitude upon exposure to analytes such as acids or bases, making it a useful material for detection of these analytes in the gas phase. The objectives of this lab are to synthesize different diameter polyaniline nanofibers and compare them as sensor materials. In this experiment…

  3. Integrated Mirco-Machined Hydrogen Gas Sensors

    SciTech Connect

    Frank DiMeoJr. Ing--shin Chen

    2005-12-15

    The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This report discusses the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a MEMS (Micro-Electro-Mechanical System) structure known as a micro-hotplate. In this project, Micro-hotplate structures were overcoated with engineered multilayers that serve as the active hydrogen-sensing layer. The change in electrical resistance of these layers when exposed to hydrogen gas was the measured sensor output. This project focused on achieving the following objectives: (1) Demonstrating the capabilities of micro-machined H2 sensors; (2) Developing an understanding of their performance; (3) Critically evaluating the utility and viability of this technology for life safety and process monitoring applications. In order to efficiently achieve these objectives, the following four tasks were identified: (1) Sensor Design and Fabrication; (2) Short Term Response Testing; (3) Long Term Behavior Investigation; (4) Systems Development. Key findings in the project include: The demonstration of sub-second response times to hydrogen; measured sensitivity to hydrogen concentrations below 200 ppm; a dramatic improvement in the sensor fabrication process and increased understanding of the processing properties and performance relationships of the devices; the development of improved sensing multilayers; and the discovery of a novel strain based hydrogen detection mechanism. The results of this program suggest that this hydrogen sensor technology has exceptional potential to meet the stringent demands of life safety applications as hydrogen utilization and infrastructure becomes more prevalent.

  4. Magnesium ferrite nanoparticles: a rapid gas sensor for alcohol

    NASA Astrophysics Data System (ADS)

    Godbole, Rhushikesh; Rao, Pratibha; Bhagwat, Sunita

    2017-02-01

    Highly porous spinel MgFe2O4 nanoparticles with a high specific surface area have been successfully synthesized by a sintering free auto-combustion technique and characterized for their structural and surface morphological properties using XRD, BET, TEM and SEM techniques. Their sensing properties to alcohol vapors viz. ethanol and methanol were investigated. The site occupation of metal ions was investigated by VSM. The as-synthesized sample shows the formation of sponge-like porous material which is necessary for gas adsorption. The gas sensing characteristics were obtained by measuring the gas response as a function of operating temperature, concentration of the gas, and the response-recovery time. The response of magnesium ferrite to ethanol and methanol vapors was compared and it was revealed that magnesium ferrite is more sensitive and selective to ethanol vapor. The sensor operates at a substantially low vapor concentration of about 1 ppm of alcohol vapors, exhibits fantastic response reproducibility, long term reliability and a very fast response and recovery property. Thus the present study explored the possibility of making rapidly responding alcohol vapor sensor based on magnesium ferrite. The sensing mechanism has been discussed in co-relation with magnetic and morphological properties. The role of occupancy of Mg2+ ions in magnesium ferrite on its gas sensing properties has also been studied and is found to influence the response of magnesium ferrite ethanol sensor.

  5. MEMS device for mass market gas and chemical sensors

    NASA Astrophysics Data System (ADS)

    Kinkade, Brian R.; Daly, James T.; Johnson, Edward A.

    2000-08-01

    Gas and chemical sensors are used in many applications. Industrial health and safety monitors allow companies to meet OSHA requirements by detecting harmful levels of toxic or combustible gases. Vehicle emissions are tested during annual inspections. Blood alcohol breathalizers are used by law enforcement. Refrigerant leak detection ensures that the Earth's ozone layer is not being compromised. Industrial combustion emissions are also monitored to minimize pollution. Heating and ventilation systems watch for high levels of carbon dioxide (CO2) to trigger an increase in fresh air exchange. Carbon monoxide detectors are used in homes to prevent poisoning from poor combustion ventilation. Anesthesia gases are monitored during a patients operation. The current economic reality is that two groups of gas sensor technologies are competing in two distinct existing market segments - affordable (less reliable) chemical reaction sensors for consumer markets and reliable (expensive) infrared (IR) spectroscopic sensors for industrial, laboratory, and medical instrumentation markets. Presently high volume mass-market applications are limited to CO detectros and on-board automotive emissions sensors. Due to reliability problems with electrochemical sensor-based CO detectors there is a hesitancy to apply these sensors in other high volume applications. Applications such as: natural gas leak detection, non-invasive blood glucose monitoring, home indoor air quality, personal/portable air quality monitors, home fire/burnt cooking detector, and home food spoilage detectors need a sensor that is a small, efficient, accurate, sensitive, reliable, and inexpensive. Connecting an array of these next generation gas sensors to wireless networks that are starting to proliferate today creates many other applications. Asthmatics could preview the air quality of their destinations as they venture out into the day. HVAC systems could determine if fresh air intake was actually better than the air

  6. Enhanced electrodes for solid state gas sensors

    DOEpatents

    Garzon, Fernando H.; Brosha, Eric L.

    2001-01-01

    A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

  7. Test Structures for Rapid Prototyping of Gas and Pressure Sensors

    NASA Technical Reports Server (NTRS)

    Buehler, M.; Cheng, L. J.; Martin, D.

    1996-01-01

    A multi-project ceramic substrate was used in developing a gas sensor and pressure sensor. The ceramic substrate cantained 36 chips with six variants including sensors, process control monitors, and an interconnect ship. Tha gas sensor is being developed as an air quality monitor and the pressure gauge as a barometer.

  8. Proximity Operations and Docking Sensor Development

    NASA Technical Reports Server (NTRS)

    Howard, Richard T.; Bryan, Thomas C.; Brewster, Linda L.; Lee, James E.

    2009-01-01

    The Next Generation Advanced Video Guidance Sensor (NGAVGS) has been under development for the last three years as a long-range proximity operations and docking sensor for use in an Automated Rendezvous and Docking (AR&D) system. The first autonomous rendezvous and docking in the history of the U.S. Space Program was successfully accomplished by Orbital Express, using the Advanced Video Guidance Sensor (AVGS) as the primary docking sensor. That flight proved that the United States now has a mature and flight proven sensor technology for supporting Crew Exploration Vehicles (CEV) and Commercial Orbital Transport Systems (COTS) Automated Rendezvous and Docking (AR&D). NASA video sensors have worked well in the past: the AVGS used on the Demonstration of Autonomous Rendezvous Technology (DART) mission operated successfully in spot mode out to 2 km, and the first generation rendezvous and docking sensor, the Video Guidance Sensor (VGS), was developed and successfully flown on Space Shuttle flights in 1997 and 1998. 12 Parts obsolescence issues prevent the construction of more AVGS units, and the next generation sensor was updated to allow it to support the CEV and COTS programs. The flight proven AR&D sensor has been redesigned to update parts and add additional capabilities for CEV and COTS with the development of the Next Generation AVGS at the Marshall Space Flight Center. The obsolete imager and processor are being replaced with new radiation tolerant parts. In addition, new capabilities include greater sensor range, auto ranging capability, and real-time video output. This paper presents some sensor hardware trades, use of highly integrated laser components, and addresses the needs of future vehicles that may rendezvous and dock with the International Space Station (ISS) and other Constellation vehicles. It also discusses approaches for upgrading AVGS to address parts obsolescence, and concepts for minimizing the sensor footprint, weight, and power requirements

  9. Dataset from chemical gas sensor array in turbulent wind tunnel.

    PubMed

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Huerta, Ramón

    2015-06-01

    The dataset includes the acquired time series of a chemical detection platform exposed to different gas conditions in a turbulent wind tunnel. The chemo-sensory elements were sampling directly the environment. In contrast to traditional approaches that include measurement chambers, open sampling systems are sensitive to dispersion mechanisms of gaseous chemical analytes, namely diffusion, turbulence, and advection, making the identification and monitoring of chemical substances more challenging. The sensing platform included 72 metal-oxide gas sensors that were positioned at 6 different locations of the wind tunnel. At each location, 10 distinct chemical gases were released in the wind tunnel, the sensors were evaluated at 5 different operating temperatures, and 3 different wind speeds were generated in the wind tunnel to induce different levels of turbulence. Moreover, each configuration was repeated 20 times, yielding a dataset of 18,000 measurements. The dataset was collected over a period of 16 months. The data is related to "On the performance of gas sensor arrays in open sampling systems using Inhibitory Support Vector Machines", by Vergara et al.[1]. The dataset can be accessed publicly at the UCI repository upon citation of [1]: http://archive.ics.uci.edu/ml/datasets/Gas+sensor+arrays+in+open+sampling+settings.

  10. Autonomous Mission Operations for Sensor Webs

    NASA Astrophysics Data System (ADS)

    Underbrink, A.; Witt, K.; Stanley, J.; Mandl, D.

    2008-12-01

    We present interim results of a 2005 ROSES AIST project entitled, "Using Intelligent Agents to Form a Sensor Web for Autonomous Mission Operations", or SWAMO. The goal of the SWAMO project is to shift the control of spacecraft missions from a ground-based, centrally controlled architecture to a collaborative, distributed set of intelligent agents. The network of intelligent agents intends to reduce management requirements by utilizing model-based system prediction and autonomic model/agent collaboration. SWAMO agents are distributed throughout the Sensor Web environment, which may include multiple spacecraft, aircraft, ground systems, and ocean systems, as well as manned operations centers. The agents monitor and manage sensor platforms, Earth sensing systems, and Earth sensing models and processes. The SWAMO agents form a Sensor Web of agents via peer-to-peer coordination. Some of the intelligent agents are mobile and able to traverse between on-orbit and ground-based systems. Other agents in the network are responsible for encapsulating system models to perform prediction of future behavior of the modeled subsystems and components to which they are assigned. The software agents use semantic web technologies to enable improved information sharing among the operational entities of the Sensor Web. The semantics include ontological conceptualizations of the Sensor Web environment, plus conceptualizations of the SWAMO agents themselves. By conceptualizations of the agents, we mean knowledge of their state, operational capabilities, current operational capacities, Web Service search and discovery results, agent collaboration rules, etc. The need for ontological conceptualizations over the agents is to enable autonomous and autonomic operations of the Sensor Web. The SWAMO ontology enables automated decision making and responses to the dynamic Sensor Web environment and to end user science requests. The current ontology is compatible with Open Geospatial Consortium (OGC

  11. Electronic Position Sensor for Power Operated Accessory

    DOEpatents

    Haag, Ronald H.; Chia, Michael I.

    2005-05-31

    An electronic position sensor for use with a power operated vehicle accessory, such as a power liftgate. The position sensor includes an elongated resistive circuit that is mounted such that it is stationary and extends along the path of a track portion of the power operated accessory. The position sensor further includes a contact nub mounted to a link member that moves within the track portion such that the contact nub is slidingly biased against the elongated circuit. As the link member moves under the force of a motor-driven output gear, the contact nub slides along the surface of the resistive circuit, thereby affecting the overall resistance of the circuit. The position sensor uses the overall resistance to provide an electronic position signal to an ECU, wherein the signal is indicative of the absolute position of the power operated accessory. Accordingly, the electronic position sensor is capable of providing an electronic signal that enables the ECU to track the absolute position of the power operated accessory.

  12. Acoustic Sensors for Fission Gas Characterization in MTR Harsh Environment

    NASA Astrophysics Data System (ADS)

    Very, F.; Rosenkrantz, E.; Fourmentel, D.; Destouches, C.; Villard, J. F.; Combette, P.; Ferrandis, J. Y.

    Our group is now working for more than 15 years, in a close partnership with CEA, on the development of acoustic sensors devoted to the characterization of fission gas release for in-pile experiments in Material Testing Reactor. First of all, we will present the main principle of the method and the result of a first succeed experiment called REMORA 3 used to differentiate helium and fission gas released kinetics under transient operating condition [1]. Then we will present our new researches involving thick film transducers produced by screen-printing process in order to propose piezoelectric structures for harsh temperature and irradiation measurements in new MTR reactor.

  13. Sol-Gel Thin Films for Plasmonic Gas Sensors.

    PubMed

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-07-13

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

  14. Sol-Gel Thin Films for Plasmonic Gas Sensors

    PubMed Central

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-01-01

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

  15. Gas Main Sensor and Communications Network System

    SciTech Connect

    Hagen Schempf

    2006-05-31

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the Northeast Gas Association (NGA), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. This projected was completed in April 2006, and culminated in the installation of more than 2 dozen GasNet nodes in both low- and high-pressure cast-iron and steel mains owned by multiple utilities in the northeastern US. Utilities are currently logging data (off-line) and monitoring data in real time from single and multiple networked sensors over cellular networks and collecting data using wireless bluetooth PDA systems. The system was designed to be modular, using in-pipe sensor-wands capable of measuring, flow, pressure, temperature, water-content and vibration. Internal antennae allowed for the use of the pipe-internals as a waveguide for setting up a sensor network to collect data from multiple nodes simultaneously. Sensor nodes were designed to be installed with low- and no-blow techniques and tools. Using a multi-drop bus technique with a custom protocol, all electronics were designed to be buriable and allow for on-board data-collection (SD-card), wireless relaying and cellular network forwarding. Installation options afforded by the design included direct-burial and external polemounted variants. Power was provided by one or more batteries, direct AC-power (Class I Div.2) and solar-array. The utilities are currently in a data-collection phase and intend to use the collected (and processed) data to make capital improvement decisions, compare it to Stoner model predictions and evaluate the use of such a system for future expansion, technology-improvement and commercialization starting later in 2006.

  16. Sensor and Actuator Needs for More Intelligent Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    Garg, Sanjay; Schadow, Klaus; Horn, Wolfgang; Pfoertner, Hugo; Stiharu, Ion

    2010-01-01

    This paper provides an overview of the controls and diagnostics technologies, that are seen as critical for more intelligent gas turbine engines (GTE), with an emphasis on the sensor and actuator technologies that need to be developed for the controls and diagnostics implementation. The objective of the paper is to help the "Customers" of advanced technologies, defense acquisition and aerospace research agencies, understand the state-of-the-art of intelligent GTE technologies, and help the "Researchers" and "Technology Developers" for GTE sensors and actuators identify what technologies need to be developed to enable the "Intelligent GTE" concepts and focus their research efforts on closing the technology gap. To keep the effort manageable, the focus of the paper is on "On-Board Intelligence" to enable safe and efficient operation of the engine over its life time, with an emphasis on gas path performance

  17. Autonomy and Sensor Webs: The Evolution of Mission Operations

    NASA Technical Reports Server (NTRS)

    Sherwood, Rob

    2008-01-01

    Demonstration of these sensor web capabilities will enable fast responding science campaigns that combine spaceborne, airborne, and ground assets. Sensor webs will also require new operations paradigms. These sensor webs will be operated directly by scientists using science goals to control their instruments. We will explore these new operations architectures through a study of existing sensor web prototypes.

  18. Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.

    ERIC Educational Resources Information Center

    Powers, Michael H.; Hull, Stacey E.

    1988-01-01

    Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)

  19. Open Path Trace Gas Laser Sensors for UAV Deployment

    NASA Astrophysics Data System (ADS)

    Shadman, S.; Mchale, L.; Rose, C.; Yalin, A.

    2015-12-01

    Novel trace gas sensors based on open-path Cavity Ring-down Spectroscopy (CRDS) are being developed to enable remote and mobile deployments including on small unmanned aerial systems (UAS). Relative to established closed-path CRDS instruments, the use of open-path configurations allows removal of the bulky and power hungry vacuum and flow system, potentially enabling lightweight and low power instruments with high sensitivity. However, open path operation introduces new challenges including the need to maintain mirror cleanliness, mitigation of particle optical effects, and the need to measure spectral features that are relatively broad. The present submission details open-path CRDS instruments for ammonia and methane and their planned use in UAS studies. The ammonia sensor uses a quantum cascade laser at 10.3 mm in a configuration in which the laser frequency is continuously swept and a trigger circuit and acousto-optic modulator (AOM) extinguish the light when the laser is resonant with the cavity. Ring-down signals are measured with a two-stage thermoelectrically cooled MCT photodetector. The cavity mirrors have reflectivity of 0.9995 and a noise equivalent absorption of 1.5 ppb Hz-1/2 was demonstrated. A first version of the methane sensor operated at 1.7um with a telecom diode laser while the current version operates at 3.6 um with an interband cascade laser (stronger absorption). We have performed validation measurements against known standards for both sensors. Compact optical assemblies are being developed for UAS deployment. For example, the methane sensor head will have target mass of <4 kg and power draw <40 W. A compact single board computer and DAQ system is being designed for sensor control and signal processing with target mass <1 kg and power draw <10 W. The sensor size and power parameters are suitable for UAS deployment on both fixed wing and rotor style UAS. We plan to deploy the methane sensor to measure leakage and emission of methane from

  20. Advanced figure sensor operations and maintenance manual

    NASA Technical Reports Server (NTRS)

    Robertson, H. J.

    1972-01-01

    This manual contains procedures for installing, operating, and maintaining the optical figure sensor and its associated electronic controls. The optical figure sensor, a system of integrated components, comprises: (1) a phase measuring modified interferometer employing a single frequency 6328 A laser, and a Vidissector; (2) a two-axis automatic thermal compensation control mount; (3) a five degree of freedom manual adjustment stand; and (4) a control console. This instrument provides real time output data of optical figure errors for spherical mirrors, and is also capable of measuring aspherical mirrors if a null corrector is added.

  1. Digital Sun Sensor Multi-Spot Operation

    PubMed Central

    Rufino, Giancarlo; Grassi, Michele

    2012-01-01

    The operation and test of a multi-spot digital sun sensor for precise sun-line determination is described. The image forming system consists of an opaque mask with multiple pinhole apertures producing multiple, simultaneous, spot-like images of the sun on the focal plane. The sun-line precision can be improved by averaging multiple simultaneous measures. Nevertheless, the sensor operation on a wide field of view requires acquiring and processing images in which the number of sun spots and the related intensity level are largely variable. To this end, a reliable and robust image acquisition procedure based on a variable shutter time has been considered as well as a calibration function exploiting also the knowledge of the sun-spot array size. Main focus of the present paper is the experimental validation of the wide field of view operation of the sensor by using a sensor prototype and a laboratory test facility. Results demonstrate that it is possible to keep high measurement precision also for large off-boresight angles. PMID:23443388

  2. Electrochemical high-temperature gas sensors

    NASA Astrophysics Data System (ADS)

    Saruhan, B.; Stranzenbach, M.; Yüce, A.; Gönüllü, Y.

    2012-06-01

    Combustion produced common air pollutant, NOx associates with greenhouse effects. Its high temperature detection is essential for protection of nature. Component-integration capable high-temperature sensors enable the control of combustion products. The requirements are quantitative detection of total NOx and high selectivity at temperatures above 500°C. This study reports various approaches to detect NO and NO2 selectively under lean and humid conditions at temperatures from 300°C to 800°C. All tested electrochemical sensors were fabricated in planar design to enable componentintegration. We suggest first an impedance-metric gas sensor for total NOx-detection consisting of NiO- or NiCr2O4-SE and PYSZ-electrolyte. The electrolyte-layer is about 200μm thickness and constructed of quasi-single crystalline columns. The sensing-electrode (SE) is magnetron sputtered thin-layers of NiO or NiCr2O4. Sensor sensitivity for detection of total NOx has been measured by applying impedance analysis. The cross-sensitivity to other emission gases such as CO, CO2, CH4 and oxygen (5 vol.%) has been determined under 0-1000ppm NO. Sensor maintains its high sensitivity at temperatures up to 550°C and 600°C, depending on the sensing-electrode. NiO-SE yields better selectivity to NO in the presence of oxygen and have shorter response times comparing to NiCr2O4-SE. For higher temperature NO2-sensing capability, a resistive DC-sensor having Al-doped TiO2-sensing layers has been employed. Sensor-sensitivity towards NO2 and cross-sensitivity to CO has been determined in the presence of H2O at temperatures 600°C and 800°C. NO2 concentrations varying from 25 to 100ppm and CO concentrations from 25 to 75ppm can be detected. By nano-tubular structuring of TiO2, NO2 sensitivity of the sensor was increased.

  3. Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

    SciTech Connect

    Kim, S; Young, C; Chan, J; Carter, C; Mizaikoff, B

    2007-07-12

    A hollow waveguide mid-infrared gas sensor operating from 1000 cm{sup -1} to 4000 cm{sup -1} has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH{sub 4} was used as test analyte during exponential dilution experiments for accurate determination of the achievable limit of detection (LOD). It is shown that the optimized integration of an optical gas sensor module with FT-IR spectroscopy provides trace sensitivity at the few hundreds of parts-per-billion concentration range (ppb, v/v) for CH{sub 4}.

  4. Utilizing the response patterns of a temperature modulated chemoresistive gas sensor for gas diagnosis

    NASA Astrophysics Data System (ADS)

    Amini, Amir; Ghafarinia, Vahid

    2011-02-01

    The observed features in the temporal response patterns of a temperature-modulated chemoresistive gas sensor were used for gas diagnosis. The patterns were recorded for clean air and air contaminated with different levels of some volatile organic compounds while a staircase heating voltage waveform had been applied to the microheater of a tin oxide gas sensor that modulated its operating temperature. Combining the steady-state and transient parameters of the recorded responses in the 50-400°C range resulted in discriminatory feature vectors which were utilized for contaminant classification. The information content of these feature vectors was proved sufficient for discrimination of methanol, ethanol, 1-butanol, and acetone contaminations in a wide concentration range.

  5. Novel Gas Sensors for High-Temperature Fossil Fuel Applications

    SciTech Connect

    Palitha Jayaweera; Francis Tanzella

    2005-03-01

    SRI International (SRI) is developing ceramic-based microsensors to detect exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems under this DOE NETL-sponsored research project. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes attached to a solid state electrolyte and are designed to operate at the high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. The sensors can be easily integrated into online monitoring systems for active emission control. The ultimate objective is to develop sensors for multiple gas detection in a single package, along with data acquisition and control software and hardware, so that the information can be used for closed-loop control in novel advanced power generation systems. This report details the Phase I Proof-of-Concept, research activities performed from October 2003 to March 2005. SRI's research work includes synthesis of catalytic materials, sensor design and fabrication, software development, and demonstration of pulse voltammetric analysis of NO, NO{sub 2}, and CO gases on catalytic electrodes.

  6. Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor

    DTIC Science & Technology

    2013-05-01

    Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor by Padraig G. Moloney and Enrique V. Barrera ARL-CR-0714 May...2013 Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor Padraig G. Moloney and Enrique V. Barrera Dept. of...From - To) June 2011 to April 2012 4. TITLE AND SUBTITLE Application of Conductive Carbon Nanotube Fibers and Composites: Gas Sensor 5a

  7. [A mobile sensor for remote detection of natural gas leakage].

    PubMed

    Zhang, Shuai; Liu, Wen-qing; Zhang, Yu-jun; Kan, Rui-feng; Ruan, Jun; Wang, Li-ming; Yu, Dian-qiang; Dong, Jin-ting; Han, Xiao-lei; Cui, Yi-ben; Liu, Jian-guo

    2012-02-01

    The detection of natural gas pipeline leak becomes a significant issue for body security, environmental protection and security of state property. However, the leak detection is difficult, because of the pipeline's covering many areas, operating conditions and complicated environment. A mobile sensor for remote detection of natural gas leakage based on scanning wavelength differential absorption spectroscopy (SWDAS) is introduced. The improved soft threshold wavelet denoising was proposed by analyzing the characteristics of reflection spectrum. And the results showed that the signal to noise ratio (SNR) was increased three times. When light intensity is 530 nA, the minimum remote sensitivity will be 80 ppm x m. A widely used SWDAS can make quantitative remote sensing of natural gas leak and locate the leak source precisely in a faster, safer and more intelligent way.

  8. Detecting changes of a distant gas source with an array of MOX gas sensors.

    PubMed

    Pashami, Sepideh; Lilienthal, Achim J; Trincavelli, Marco

    2012-11-27

    We address the problem of detecting changes in the activity of a distant gas source from the response of an array of metal oxide (MOX) gas sensors deployed in an open sampling system. The main challenge is the turbulent nature of gas dispersion and the response dynamics of the sensors. We propose a change point detection approach and evaluate it on individual gas sensors in an experimental setup where a gas source changes in intensity, compound, or mixture ratio. We also introduce an efficient sensor selection algorithm and evaluate the change point detection approach with the selected sensor array subsets.

  9. Membrane-Based Characterization of a Gas Component — A Transient Sensor Theory

    PubMed Central

    Lazik, Detlef

    2014-01-01

    Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions. PMID:24608004

  10. The oil and gas joint operating agreement

    SciTech Connect

    Not Available

    1990-01-01

    This book covers the following topics: introduction to the AAPL model form operating agreement; property provisions of the operating agreement; Article 6---the drilling and development article; duties and obligations revisited---who bear what risk of loss; operator's liens; accounting procedure joint operations; insurance; taking gas in kind absent a balancing agreement; RMMLF Form 5 Gas Balancing Agreement; tax partnerships for nontax professionals; alternative agreement forms.

  11. Selective Sensing of Gas Mixture via a Temperature Modulation Approach: New Strategy for Potentiometric Gas Sensor Obtaining Satisfactory Discriminating Features

    PubMed Central

    Li, Fu-an; Jin, Han; Wang, Jinxia; Zou, Jie; Jian, Jiawen

    2017-01-01

    A new strategy to discriminate four types of hazardous gases is proposed in this research. Through modulating the operating temperature and the processing response signal with a pattern recognition algorithm, a gas sensor consisting of a single sensing electrode, i.e., ZnO/In2O3 composite, is designed to differentiate NO2, NH3, C3H6, CO within the level of 50–400 ppm. Results indicate that with adding 15 wt.% ZnO to In2O3, the sensor fabricated at 900 °C shows optimal sensing characteristics in detecting all the studied gases. Moreover, with the aid of the principle component analysis (PCA) algorithm, the sensor operating in the temperature modulation mode demonstrates acceptable discrimination features. The satisfactory discrimination features disclose the future that it is possible to differentiate gas mixture efficiently through operating a single electrode sensor at temperature modulation mode. PMID:28287492

  12. Video Guidance Sensor for Surface Mobility Operations

    NASA Technical Reports Server (NTRS)

    Fernandez, Kenneth R.; Fischer, Richard; Bryan, Thomas; Howell, Joe; Howard, Ricky; Peters, Bruce

    2008-01-01

    Robotic systems and surface mobility will play an increased role in future exploration missions. Unlike the LRV during Apollo era which was an astronaut piloted vehicle future systems will include teleoperated and semi-autonomous operations. The tasks given to these vehicles will run the range from infrastructure maintenance, ISRU, and construction to name a few. A common task that may be performed would be the retrieval and deployment of trailer mounted equipment. Operational scenarios may require these operations to be performed remotely via a teleoperated mode,or semi-autonomously. This presentation describes the on-going project to adapt the Automated Rendezvous and Capture (AR&C) sensor developed at the Marshall Space Flight Center for use in an automated trailer pick-up and deployment operation. The sensor which has been successfully demonstrated on-orbit has been mounted on an iRobot/John Deere RGATOR autonomous vehicle for this demonstration which will be completed in the March 2008 time-frame.

  13. Chemical Gas Sensors for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Liu, C. C.

    1998-01-01

    Chemical sensors often need to be specifically designed (or tailored) to operate in a given environment. It is often the case that a chemical sensor that meets the needs of one application will not function adequately in another application. The more demanding the environment and specialized the requirement, the greater the need to adapt exiting sensor technologies to meet these requirements or, as necessary, develop new sensor technologies. Aerospace (aeronautic and space) applications are particularly challenging since often these applications have specifications which have not previously been the emphasis of commercial suppliers. Further, the chemical sensing needs of aerospace applications have changed over the years to reflect the changing emphasis of society. Three chemical sensing applications of particular interest to the National Aeronautics and Space Administration (NASA) which illustrate these trends are launch vehicle leak detection, emission monitoring, and fire detection. Each of these applications reflects efforts ongoing throughout NASA. As described in NASA's "Three Pillars for Success", a document which outlines NASA's long term response to achieve the nation's priorities in aerospace transportation, agency wide objectives include: improving safety and decreasing the cost of space travel, significantly decreasing the amount of emissions produced by aeronautic engines, and improving the safety of commercial airline travel. As will be discussed below, chemical sensing in leak detection, emission monitoring, and fire detection will help enable the agency to meet these objectives. Each application has vastly different problems associated with the measurement of chemical species. Nonetheless, the development of a common base technology can address the measurement needs of a number of applications.

  14. Polycrystalline-silicon microbridge combustible gas sensor

    NASA Astrophysics Data System (ADS)

    Manginell, Ronald Paul

    Catalytic, calorimetric gas detection is the most commonly used method for the detection of combustible gases below the lower-explosive limit (LEL). In this method, the heat of oxidation of a combustible species on a heated catalyst surface is detected by a resistance thermometer in proximity. Conventionally fabricated sensors suffer from high-power consumption (˜500 mW), slow thermal response (˜15 sec) and low thermal sensitivity (1-2sp°C/mW). Fully CMOS-compatible, surface-micromachined polysilicon bridges have been fabricated for use in catalytic, calorimetric gas detection and are characterized by low-power consumption (35 mW), fast response (0.2 msec) and high sensitivity (16sp°C/mW). The batch fabrication techniques used here significantly increase the manufacturability of these devices as compared with their conventional predecessors, since hand manufacture/sorting conventionally used ate eliminated. A post-processing, post-packaging micro-chemical-vapor-deposition technique was developed for the purpose of selectively depositing catalytic films only in the active area of the sensor. Film microstructure was modified using a pulsed-deposition technique and in situ methods of film growth monitoring were investigated. With a Pt catalyst, ultimate device sensitivity to hydrogen was 100 ppm in air. To predict device response, knowledge of the temperature distribution along a microbridge is required. Both analytical and numerical techniques were used to model this distribution and are in good agreement with measurements obtained by infrared microscopy, For modeling purposes the temperature dependence of the thermal and electrical conductivity of polysilicon at high temperature ({>}300sp°C) were measured using microbridges outfitted with special high-temperature bond pads. Physical models of thermal and electrical conduction in polysilicon were constructed.

  15. Advancement of Miniature Optic Gas Sensor (MOGS) Probe Technology

    NASA Technical Reports Server (NTRS)

    Chullen, Cinda

    2015-01-01

    Advancement of Miniature Optic Gas Sensor (MOGS) Probe Technology" project will investigate newly developed optic gas sensors delivered from a Small Business Innovative Research (SBIR) Phase II effort. A ventilation test rig will be designed and fabricated to test the sensors while integrated with a Suited Manikin Test Apparatus (SMTA). Once the sensors are integrated, a series of test points will be completed to verify that the sensors can withstand Advanced Suit Portable Life Support System (PLSS) environments and associated human metabolic profiles for changes in pressure and levels of Oxygen (ppO2), carbon dioxide (ppCO2), and humidity (ppH2O).

  16. Novel strategies for development of gas sensors for combustion and medical applications

    NASA Astrophysics Data System (ADS)

    Fulmer, Adam; Mullen, Max; Sun, Chenhu; Dutta, Prabir K.

    2014-06-01

    Chemical gas sensors can have an enormous impact on optimizing complex processes as well as facilitate disease diagnosis. In this article, we demonstrate how sensing of gas molecules is influencing the next generation of engines for transportation applications, as well as in disease diagnosis. In such applications, the demands on sensors are quite extreme. Not only does the device have to detect the gas of interest with high sensitivity, it also has to discriminate against other species present in a complex environment, such as combustion exhaust and human breath. In addition, the sensors will need to have as small a footprint as possible in size and power requirements. With these varied requirements in mind, only electrochemical sensors have the potential to be practical. This article focuses on nitric oxide (NOx) and ammonia (NH3) sensor necessary for emission control of next generation, high efficiency, lean burn engines and nitric oxide (NO) sensor for breath analysis for diagnosis of respiratory diseases. In all of these applications, there has been significant recent commercial activity. We indicate the electrochemical principles of these commercial sensors, and the development from our research group. We present potentiometric total NOx sensors that can operate in harsh environments, and impedance-based NH3 sensor for transportation industry. For detecting NO in human breath, we have demonstrated two strategies, the first using a resistive approach, and the second with an array of potentiometric sensors. Data from these sensors, their limitations as well as novel MEMS-based approaches for miniaturization is presented.

  17. Sensor-web Operations Explorer (SOX)

    NASA Astrophysics Data System (ADS)

    Lee, M.; Weidner, R.; Bowman, K.; Sandu, A.; Singh, K.

    2008-12-01

    The Sensor-web Operations Explorer (SOX) is a research task under the Advanced Information Systems Technology project of the National Aeronautics and Space Administration (NASA). The objective of SOX is to develop an integrated software infrastructure (combining air-quality observations with models and data- assimilation tools) that permits a focused analysis of the chemical state and that can adapt to meteorological and chemical "events" over daily time scales. Processes governing the distribution and evolution of trace gases and aerosols have a profound impact on air quality and climate. Trace gases and aerosols do not only affect air quality, but they may also impact regional and global climate through longer-lived greenhouse gases, e.g., O3, CO2, and CH4 Aerosols can have a net cooling or heating effect depending on their type and vertical distribution. The quantification of these processes requires an integrated approach that combines observations from satellites, aircraft, sondes, and surface measurements with chemistry and transport models acting on both regional and global scales. The integrated observation is approached in two modes, an exploratory observation mode and a targeted observation mode. Currently, the exploratory observation mode is fully supported by the SOX on-line service employing a concept-design and an observing system simulation experiments (OSSE) framework. The exploration process needs to be iterated for maturation of a complex sensor-web operation scenario design. For the targeted observation mode, a 4D-variational adjoint framework is being developed in collaboration with the Global Earth Observation System for Chemistry (GEOS-Chem) research teams at Jet Propulsion Laboratory and Havard University. In addition to remote sensing, advances in global chemistry and transport models (along with 4-D variational assimilation techniques) provide powerful tools for the development of sensor webs that could, in principle, be deployed at

  18. The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance

    PubMed Central

    Bakrania, Smitesh D.; Wooldridge, Margaret S.

    2009-01-01

    This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis. PMID:22399977

  19. Epoxy-free high-temperature fiber optic pressure sensors for gas turbine engine applications

    NASA Astrophysics Data System (ADS)

    Xu, Juncheng; Pickrell, Gary; Yu, Bing; Han, Ming; Zhu, Yizheng; Wang, Xingwei; Cooper, Kristie L.; Wang, Anbo

    2004-12-01

    Pressure measurements at various locations of a gas turbine engine are highly desirable to improve the operational performance and reliability. However, measurement of dynamic pressure (1psi (6.9kPa) variation superimposed on the static bias) in the operating environment of the engine, where temperatures might exceed 600°C and pressures might exceed 100psi (690kPa), is a great challenge to currently available sensors. To meet these requirements, a novel type of fiber optic engine pressure sensor has been developed. This pressure sensor functions as a diaphragm-based extrinsic Fabry-Perot interferometric (EFPI) sensor. The structure of the sensor head, composed entirely of fused silica, allows a much higher operating temperature to be achieved in conjunction with a low temperature dependence. The sensor head and the fiber tail have been packaged in a metal fitting connected to a piece of metal extension tubing, which improves the mechanical strength of the sensor and facilitates easy sensor installation. The sensor exhibited very good performance in an engine field test, demonstrating not only that the sensors' package is robust enough for engine operation, but also that its performance is consistent with that of a commercial Kulite sensor.

  20. Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

    PubMed Central

    Wang, Chengxiang; Yin, Longwei; Zhang, Luyuan; Xiang, Dong; Gao, Rui

    2010-01-01

    Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. PMID:22294916

  1. GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM

    SciTech Connect

    Hagen Schempf, Ph.D.

    2003-02-27

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. A prototype system was built for low-pressure cast-iron mains and tested in a spider- and serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The prototype unit combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-slave architecture to collect data from a distributed spider-arrangement, and in a master-repeater-slave configuration in serial or ladder-network arrangements. It was found that the system was capable of performing all data-sampling and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and valuable data was collected in order to determine how to improve on range and data-quality in the future.

  2. One-dimensional nanostructure field-effect sensors for gas detection.

    PubMed

    Zhao, Xiaoli; Cai, Bin; Tang, Qingxin; Tong, Yanhong; Liu, Yichun

    2014-07-31

    Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated.

  3. One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection

    PubMed Central

    Zhao, Xiaoli; Cai, Bin; Tang, Qingxin; Tong, Yanhong; Liu, Yichun

    2014-01-01

    Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated. PMID:25090418

  4. Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.

    PubMed

    Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook

    2014-03-15

    Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C.

  5. Application of Ionic Liquids in Amperometric Gas Sensors.

    PubMed

    Gębicki, Jacek; Kloskowski, Adam; Chrzanowski, Wojciech; Stepnowski, Piotr; Namiesnik, Jacek

    2016-01-01

    This article presents an analysis of available literature data on metrological parameters of the amperometric gas sensors containing ionic liquids as an electrolyte. Four mechanism types of signal generation in amperometric sensors with ionic liquid are described. Moreover, this article describes the influence of selected physico-chemical properties of the ionic liquids on the metrological parameters of these sensors. Some metrological parameters are also compared for amperometric sensors with GDE and SPE electrodes and with ionic liquids for selected analytes.

  6. Metal Sulfides as Sensing Materials for Chemoresistive Gas Sensors

    PubMed Central

    Gaiardo, Andrea; Fabbri, Barbara; Guidi, Vincenzo; Bellutti, Pierluigi; Giberti, Alessio; Gherardi, Sandro; Vanzetti, Lia; Malagù, Cesare; Zonta, Giulia

    2016-01-01

    This work aims at a broad overview of the results obtained with metal-sulfide materials in the field of chemoresistive gas sensing. Indeed, despite the well-known electrical, optical, structural and morphological features previously described in the literature, metal sulfides present lack of investigation for gas sensing applications, a field in which the metal oxides still maintain a leading role owing to their high sensitivity, low cost, small dimensions and simple integration, in spite of the wide assortment of sensing materials. However, despite their great advantages, metal oxides have shown significant drawbacks, which have led to the search for new materials for gas sensing devices. In this work, Cadmium Sulfide and Tin (IV) Sulfide were investigated as functional materials for thick-film chemoresistive gas-sensors fabrication and they were tested both in thermo- and in photo-activation modes. Furthermore, electrical characterization was carried out in order to verify their gas sensing properties and material stability, by comparing the results obtained with metal sulfides to those obtained by using their metal-oxides counterparts. The results highlighted the possibility to use metal sulfides as a novel class of sensing materials, owing to their selectivity to specific compounds, stability, and the possibility to operate at room temperature. PMID:26927120

  7. Gas sensors using single layer patterned interference optical filters

    NASA Astrophysics Data System (ADS)

    Rahmlow, Thomas D.; Gallagher, Kieran; Johnson, Robert L.

    2016-03-01

    A method for fabricating filters for fiber optic sensors is presented. The interference filter's construction is laid on it's side to allow for the use of air as the low refractive index material. Bandpass filters tuned to the absorption line of a trace gas can then be used as a sensitive means of detecting gas concentration. Complex filter designs can be fabricated in a single patterned layer. A CO2/CH4 gas sensor is presented as a design example.

  8. IR sensors and imagers in networked operations

    NASA Astrophysics Data System (ADS)

    Breiter, Rainer; Cabanski, Wolfgang

    2005-05-01

    "Network-centric Warfare" is a common slogan describing an overall concept of networked operation of sensors, information and weapons to gain command and control superiority. Referring to IR sensors, integration and fusion of different channels like day/night or SAR images or the ability to spread image data among various users are typical requirements. Looking for concrete implementations the German Army future infantryman IdZ is an example where a group of ten soldiers build a unit with every soldier equipped with a personal digital assistant (PDA) for information display, day photo camera and a high performance thermal imager for every unit. The challenge to allow networked operation among such a unit is bringing information together and distribution over a capable network. So also AIM's thermal reconnaissance and targeting sight HuntIR which was selected for the IdZ program provides this capabilities by an optional wireless interface. Besides the global approach of Network-centric Warfare network technology can also be an interesting solution for digital image data distribution and signal processing behind the FPA replacing analog video networks or specific point to point interfaces. The resulting architecture can provide capabilities of data fusion from e.g. IR dual-band or IR multicolor sensors. AIM has participated in a German/UK collaboration program to produce a demonstrator for day/IR video distribution via Gigabit Ethernet for vehicle applications. In this study Ethernet technology was chosen for network implementation and a set of electronics was developed for capturing video data of IR and day imagers and Gigabit Ethernet video distribution. The demonstrator setup follows the requirements of current and future vehicles having a set of day and night imager cameras and a crew station with several members. Replacing the analog video path by a digital video network also makes it easy to implement embedded training by simply feeding the network with

  9. Portable organic gas detection sensor based on the effect of guided-mode resonance

    NASA Astrophysics Data System (ADS)

    Guo, Liang; Wang, Qi; Huang, Yuanshen; Zhang, Dawei

    2017-01-01

    A novel organic gas detection sensor based on the effect of guided-mode resonance is proposed in this paper. The sensor is designed to operate in the visible light band. It contains four main sections: a light source, a miniature gas chamber composed of a guided-mode resonant filter, a diffraction grating, and a CCD image sensor. When bunched visible light is irradiated vertically to the gas chamber, it passes through the gas chamber and diffraction grating, and is then received by the CCD sensor. The optical signal received by the CCD sensor is then reduced to the spectrum using a specific algorithm. When organic gases are injected into the gas chamber, there is a shift in the wavelength of resonant reflection, and the magnitude of this shift is proportional to the refractive index of the gas. The large variation in the refractive indexes of industrially important organic gases means that their characteristic peak wavelengths can be easily identified. As a result, this system can quickly detect organic gases. To verify the feasibility of this technique, we use finite difference time domain solutions to simulate the results. The sensitivity of this type of sensor can reach wavelength differences of 0.001 nm, which means that the sensor has high potential for application in portable, high-precision detection systems.

  10. Ammonia gas sensor based on electrosynthesized polypyrrole films.

    PubMed

    Carquigny, Stéphanie; Sanchez, Jean-Baptiste; Berger, Franck; Lakard, Boris; Lallemand, Fabrice

    2009-04-15

    In this work, design and fabrication of micro-gas-sensors, polymerization and deposition of poly(pyrrole) thin films as sensitive layer for the micro-gas-sensors by electrochemical processing, and characterization of the polymer films by FTIR, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), are reported. The change in conductance of thin polymer layers is used as a sensor signal. The behaviours, including sensitivity, reproducibility and reversibility, to various ammonia gas concentrations ranging from 8 ppm to 1000 ppm are investigated. The influence of the temperature on the electrical response of the sensors is also studied. The experimental results show that these ammonia gas sensors are efficient since they are sensitive to ammonia, reversible and reproducible at room temperature.

  11. Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.

    2005-01-01

    Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, and fire detection. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors; 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity; 3) The development of high temperature semiconductors, especially silicon carbide. This presentation discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

  12. Varying potential silicon carbide gas sensor

    NASA Technical Reports Server (NTRS)

    Shields, Virgil B. (Inventor); Ryan, Margaret A. (Inventor); Williams, Roger M. (Inventor)

    1997-01-01

    A hydrocarbon gas detection device operates by dissociating or electro-chemically oxidizing hydrocarbons adsorbed to a silicon carbide detection layer. Dissociation or oxidation are driven by a varying potential applied to the detection layer. Different hydrocarbon species undergo reaction at different applied potentials so that the device is able to discriminate among various hydrocarbon species. The device can operate at temperatures between 100.degree. C. and at least 650.degree. C., allowing hydrocarbon detection in hot exhaust gases. The dissociation reaction is detected either as a change in a capacitor or, preferably, as a change of current flow through an FET which incorporates the silicon carbide detection layers. The silicon carbide detection layer can be augmented with a pad of catalytic material which provides a signal without an applied potential. Comparisons between the catalytically produced signal and the varying potential produced signal may further help identify the hydrocarbon present.

  13. Chemical Gas Sensors for Aeronautic and Space Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

    1997-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Two areas of particular interest are safety monitoring and emission monitoring. In safety monitoring, detection of low concentrations of hydrogen at potentially low temperatures is important while for emission monitoring the detection of nitrogen oxides, hydrogen, hydrocarbons and oxygen is of interest. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: (1) Micromachining and microfabrication technology to fabricate miniaturized sensors. (2) The development of high temperature semiconductors, especially silicon carbide. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this general area of sensor development a field of significant interest.

  14. Fabrication and characterization of SnO2/ZnO gas sensors for detecting toluene gas.

    PubMed

    Min, Byung-Sam; Park, Young-Ho; Lee, Chang-Seop

    2014-11-01

    This study investigates the use of SnO2, ZnO, Ag, Au, Cu, In, Pd, Ru and carbon black to improve the sensitivity of a gas sensor for detecting toluene gas. Metal-SnO2/ZnO thick films were screen-printed onto Al2O3 substrates with platinum electrodes. The physico-chemical properties of the sensor materials were characterized using SEM/EDS, XRD, and BET analyses. Measuring the electrical resistance of each sensor as a function of the gas concentration determined the sensing characteristics. The sensors were tested using toluene, benzene, xylene, ethanol, methanol, ammonia and trimethylamine vapors with concentrations of 1-2000 ppm. The gas sensing properties of metal-SnO2/ZnO thick films depended on the content and variety of metals and the content of carbon black. The optimum condition of sensor material for toluene gas detection is operation temperature 300 degrees C and when metal catalyst Cu and carbon black were added. The best sensitivity and selectivity for toluene gas at 300 degrees C resulted from doping with 5 wt.% carbon black, 1 wt.% Cu and 20 wt.% ZnO to SnO2.

  15. GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM

    SciTech Connect

    Hagen Schempf

    2004-09-30

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. In Phase II of this three-phase program, an improved prototype system was built for low-pressure cast-iron and high-pressure steel (including a no-blow installation system) mains and tested in a serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The experiment was carried out in several open-hole excavations over a multi-day period. The prototype units (3 total) combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-repeater-slave configuration in serial or ladder-network arrangements. It was verified that the system was capable of performing all data-sampling, data-storage and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and the system was demonstrated to run off in-ground battery- and above-ground solar power. The remote datalogger access and storage-card features were demonstrated and used to log and post-process system data. Real-time data-display on an updated Phase-I GUI was used for in-field demonstration and troubleshooting.

  16. Operating a fuel cell using landfill gas

    SciTech Connect

    Trippel, C.E.; Preston, J.L. Jr.; Trocciola, J.; Spiegel, R.

    1996-12-31

    An ONSI PC25{trademark}, 200 kW (nominal capacity) phosphoric acid fuel cell operating on landfill gas is installed at the Town of Groton Flanders Road landfill in Groton, Connecticut. This joint project by the Connecticut Light & Power Company (CL&P) which is an operating company of Northeast Utilities, the Town of Groton, International Fuel Cells (IFC), and the US EPA is intended to demonstrate the viability of installing, operating and maintaining a fuel cell operating on landfill gas at a landfill site. The goals of the project are to evaluate the fuel cell and gas pretreatment unit operation, test modifications to simplify the GPU design and demonstrate reliability of the entire system.

  17. Redesigned Gas Mass Flow Sensors for Space Shuttle Pressure Control System and Fuel Cell System

    NASA Technical Reports Server (NTRS)

    1996-01-01

    A program was conducted to determine if a state of the art micro-machined silicon solid state flow sensor could be used to replace the existing space shuttle orbiter flow sensors. The rather aggressive goal was to obtain a new sensor which would also be a multi-gas sensor and operate over a much wider flow range and with a higher degree of accuracy than the existing sensors. Two types of sensors were tested. The first type was a venturi throat design and the second was a bypass design. The accuracy of venturi design was found to be marginally acceptable. The bypass sensor was much better although it still did not fully reach the accuracy goal. Two main problems were identified which would require further work.

  18. Basic gas storage reservoir operations and analysis

    SciTech Connect

    Nowaczewski, S.F. )

    1994-08-01

    Operation and performance analysis of gas storage reservoirs is described in very basic and general terms. Reservoir selection criteria (capacity, deliverability, location, field type, trap type) are reviewed. Well construction considerations and practices (casing sizing, placement, and cementing) are highlighted with regard to the need for long-lived safe operation. Deliverability estimation and prediction and gas inventory methodologies are described. The benefits of high density, high quality data on gas pressure and composition, production rates and volumes, and geologic information to reservoir performance evaluation and prediction are demonstrated.

  19. Triboelectric Hydrogen Gas Sensor with Pd Functionalized Surface

    PubMed Central

    Shin, Sung-Ho; Kwon, Yang Hyeog; Kim, Young-Hwan; Jung, Joo-Yun; Nah, Junghyo

    2016-01-01

    Palladium (Pd)-based hydrogen (H2) gas sensors have been widely investigated thanks to its fast reaction and high sensitivity to hydrogen. Various sensing mechanisms have been adopted for H2 gas sensors; however, all the sensors must be powered through an external battery. We report here an H2 gas sensor that can detect H2 by measuring the output voltages generated during contact electrification between two friction surfaces. When the H2 sensor, composed of Pd-coated ITO (indium tin oxide) and PET (polyethylene Terephthalate) film, is exposed to H2, its output voltage is varied in proportion to H2 concentration because the work function (WF) of Pd-coated surface changes, altering triboelectric charging behavior. Specifically, the output voltage of the sensor is gradually increased as exposing H2 concentration increases. Reproducible and sensitive sensor response was observed up 1% H2 exposure. The approach introduced here can easily be adopted to development of triboelectric gas sensors detecting other gas species. PMID:28335313

  20. Compressive hyperspectral sensor for LWIR gas detection

    NASA Astrophysics Data System (ADS)

    Russell, Thomas A.; McMackin, Lenore; Bridge, Bob; Baraniuk, Richard

    2012-06-01

    Focal plane arrays with associated electronics and cooling are a substantial portion of the cost, complexity, size, weight, and power requirements of Long-Wave IR (LWIR) imagers. Hyperspectral LWIR imagers add significant data volume burden as they collect a high-resolution spectrum at each pixel. We report here on a LWIR Hyperspectral Sensor that applies Compressive Sensing (CS) in order to achieve benefits in these areas. The sensor applies single-pixel detection technology demonstrated by Rice University. The single-pixel approach uses a Digital Micro-mirror Device (DMD) to reflect and multiplex the light from a random assortment of pixels onto the detector. This is repeated for a number of measurements much less than the total number of scene pixels. We have extended this architecture to hyperspectral LWIR sensing by inserting a Fabry-Perot spectrometer in the optical path. This compressive hyperspectral imager collects all three dimensions on a single detection element, greatly reducing the size, weight and power requirements of the system relative to traditional approaches, while also reducing data volume. The CS architecture also supports innovative adaptive approaches to sensing, as the DMD device allows control over the selection of spatial scene pixels to be multiplexed on the detector. We are applying this advantage to the detection of plume gases, by adaptively locating and concentrating target energy. A key challenge in this system is the diffraction loss produce by the DMD in the LWIR. We report the results of testing DMD operation in the LWIR, as well as system spatial and spectral performance.

  1. Chemical Gas Sensors for Aeronautic and Space Applications 2

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Chen, L. Y.; Neudeck, P. G.; Knight, D.; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, D.; Liu, M.; Rauch, W. A.

    1998-01-01

    Aeronautic and Space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of most interest include launch vehicle safety monitoring emission monitoring and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensor is based on progress two types of technology: 1) Micro-machining and micro-fabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this micro-fabricated gas sensor technology make this area of sensor development a field of significant interest.

  2. Chemical Gas Sensors for Aeronautic and Space Applications 2

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liong-Yu; Neudeck, Phil G.; Knight, Dale; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, Darby; Liu, M.; Rauch, W. A.

    1998-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of interest include launch vehicle safety monitoring, emission monitoring, and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this area of sensor development a field of significant interest.

  3. Chemical Gas Sensors for Aeronautics and Space Applications III

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Chen, L. Y.; Liu, C. C.; Wu, Q. H.; Sawayda, M. S.; Jin, Z.; Hammond, J.; Makel, D.; Liu, M.; Rauch, W. A.; Hall, G.

    1999-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of interest include launch vehicle safety monitoring, emission monitoring, and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this area of sensor development a field of significant interest.

  4. Pulse-driven micro gas sensor fitted with clustered Pd/SnO2 nanoparticles.

    PubMed

    Suematsu, Koichi; Shin, Yuka; Ma, Nan; Oyama, Tokiharu; Sasaki, Miyuki; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

    2015-08-18

    Real-time monitoring of specific gas concentrations with a compact and portable gas sensing device is required to sense potential health risk and danger from toxic gases. For such purposes, we developed an ultrasmall gas sensor device, where a micro sensing film was deposited on a micro heater integrated with electrodes fabricated by the microelectromechanical system (MEMS) technology. The developed device was operated in a pulse-heating mode to significantly reduce the heater power consumption and make the device battery-driven and portable. Using clustered Pd/SnO2 nanoparticles, we succeeded in introducing mesopores ranging from 10 to 30 nm in the micro gas sensing film (area: ϕ 150 μm) to detect large volatile organic compounds (VOCs). The micro sensor showed quick, stable, and high sensor responses to toluene at ppm (parts per million) concentrations at 300 °C even by operating the micro heater in a pulse-heating mode where switch-on and -off cycles were repeated at one-second intervals. The high performance of the micro sensor should result from the creation of efficient diffusion paths decorated with Pd sensitizers by using the clustered Pd/SnO2 nanoparticles. Hence we demonstrate that our pulse-driven micro sensor using nanostructured oxide materials holds promise as a battery-operable, portable gas sensing device.

  5. Gas Sensors Based on Polymer Field-Effect Transistors

    PubMed Central

    Lv, Aifeng; Pan, Yong; Chi, Lifeng

    2017-01-01

    This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD). Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance. Most importantly, we summarize various analyte–polymer interactions, which help to understand the sensing mechanism in the PFET sensors and can provide possible approaches for the sensor fabrication in the future. PMID:28117760

  6. Features extraction from the electrocatalytic gas sensor responses

    NASA Astrophysics Data System (ADS)

    Kalinowski, Paweł; Woźniak, Łukasz; Stachowiak, Maria; Jasiński, Grzegorz; Jasiński, Piotr

    2016-11-01

    One of the types of gas sensors used for detection and identification of toxic-air pollutant is an electro-catalytic gas sensor. The electro-catalytic sensors are working in cyclic voltammetry mode, enable detection of various gases. Their response are in the form of I-V curves which contain information about the type and the concentration of measured volatile compound. However, additional analysis is required to provide the efficient recognition of the target gas. Multivariate data analysis and pattern recognition methods are proven to be useful tool for such application, but further investigations on the improvement of the sensor's responses processing are required. In this article the method for extraction of the parameters from the electro-catalytic sensor responses is presented. Extracted features enable the significant reduction of data dimension without the loss of the efficiency of recognition of four volatile air-pollutant, namely nitrogen dioxide, ammonia, hydrogen sulfide and sulfur dioxide.

  7. Gas Sensors Based on Polymer Field-Effect Transistors.

    PubMed

    Lv, Aifeng; Pan, Yong; Chi, Lifeng

    2017-01-22

    This review focuses on polymer field-effect transistor (PFET) based gas sensor with polymer as the sensing layer, which interacts with gas analyte and thus induces the change of source-drain current (ΔISD). Dependent on the sensing layer which can be semiconducting polymer, dielectric layer or conducting polymer gate, the PFET sensors can be subdivided into three types. For each type of sensor, we present the molecular structure of sensing polymer, the gas analyte and the sensing performance. Most importantly, we summarize various analyte-polymer interactions, which help to understand the sensing mechanism in the PFET sensors and can provide possible approaches for the sensor fabrication in the future.

  8. Hydrate Control for Gas Storage Operations

    SciTech Connect

    Jeffrey Savidge

    2008-10-31

    The overall objective of this project was to identify low cost hydrate control options to help mitigate and solve hydrate problems that occur in moderate and high pressure natural gas storage field operations. The study includes data on a number of flow configurations, fluids and control options that are common in natural gas storage field flow lines. The final phase of this work brings together data and experience from the hydrate flow test facility and multiple field and operator sources. It includes a compilation of basic information on operating conditions as well as candidate field separation options. Lastly the work is integrated with the work with the initial work to provide a comprehensive view of gas storage field hydrate control for field operations and storage field personnel.

  9. U. S. gas pipelines improve operations

    SciTech Connect

    True, W.R.

    1990-11-26

    This paper discusses how operations for regulated U.S. interstate natural-gas pipeline companies showed increased efficiency last year as incomes leaped despite flat revenues. Net incomes for these companies gained more than $900 million in 1989, while operating revenues declined a negligible 1.2%. Common-carrier oil pipelines, on the other hand, continued to operate in the doldrums with incomes declining for the third straight year and revenues dropping for the sixth year in a row.

  10. Novel gas sensors based on carbon nanotube networks

    NASA Astrophysics Data System (ADS)

    Sayago, I.; Terrado, E.; Aleixandre, M.; Horrillo, M. C.; Fernandez, M. J.; Lafuente, E.; Maser, W. K.; Benito, A. M.; Urriolabeitia, E. P.; Navarro, R.; Martinez, M. T.; Gutierrez, J.; Muñoz, E.

    2008-08-01

    Novel resistive gas sensors based on single-walled carbon nanotube (SWNT) networks as the active sensing element nave been investigated for gas detection. SWNTs networks were fabricated by airbrushing on alumina substrates. As-produced- and Pd-decorated SWNT materials were used as sensitive layers for the detection of NO2 and H2, respectively. The studied sensors provided good response to NO2 and H2 as well as excellent selectivities to interfering gases.

  11. The Development of Miniaturization Infrared Exhaust Gas Sensor

    NASA Astrophysics Data System (ADS)

    Chen, Hongyan; Zhang, Bing; Li, Zhibin; Liu, Wenzhen

    In order to solve the environmental pollution caused by motor vehicle exhaust, this article designed and developed a miniaturized infrared exhaust gas sensor, can effectively detect the concentration of CO2, CO, hydrocarbons, solves the existing sensor of large volume, slow response, etc.

  12. An electrochemical sensor for determining elemental iodine in gas media

    SciTech Connect

    Goffman, V.G.; Shaimerdinov, B.U.; Kotelkin, I.M.

    1993-12-01

    The possibility of using solid-electrolyte Ag, AgI/AgI/Au cells as sensors for determining the concentration of elemental iodine in gas media is investigated. It is established that the sensor parameters are independent of oxygen content and radiation dose at different relative humidities.

  13. Small battery operated unattended radar sensor for security systems

    NASA Astrophysics Data System (ADS)

    Plummer, Thomas J.; Brady, Stephen; Raines, Robert

    2013-06-01

    McQ has developed, tested, and is supplying to Unattended Ground Sensor (UGS) customers a new radar sensor. This radar sensor is designed for short range target detection and classification. The design emphasis was to have low power consumption, totally automated operation, a very high probability of detection coupled with a very low false alarm rate, be able to locate and track targets, and have a price compatible with the UGS market. The radar sensor complements traditional UGS sensors by providing solutions for scenarios that are difficult for UGS. The design of this radar sensor and the testing are presented in this paper.

  14. Approach for Self-Calibrating CO₂ Measurements with Linear Membrane-Based Gas Sensors.

    PubMed

    Lazik, Detlef; Sood, Pramit

    2016-11-17

    Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO₂ in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO₂ analysis in dry air with tubular PDMS membranes for various CO₂ concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1%) of the non-calibrated sensor response, and comparable statistical uncertainty.

  15. Approach for Self-Calibrating CO2 Measurements with Linear Membrane-Based Gas Sensors

    PubMed Central

    Lazik, Detlef; Sood, Pramit

    2016-01-01

    Linear membrane-based gas sensors that can be advantageously applied for the measurement of a single gas component in large heterogeneous systems, e.g., for representative determination of CO2 in the subsurface, can be designed depending on the properties of the observation object. A resulting disadvantage is that the permeation-based sensor response depends on operating conditions, the individual site-adapted sensor geometry, the membrane material, and the target gas component. Therefore, calibration is needed, especially of the slope, which could change over several orders of magnitude. A calibration-free approach based on an internal gas standard is developed to overcome the multi-criterial slope dependency. This results in a normalization of sensor response and enables the sensor to assess the significance of measurement. The approach was proofed on the example of CO2 analysis in dry air with tubular PDMS membranes for various CO2 concentrations of an internal standard. Negligible temperature dependency was found within an 18 K range. The transformation behavior of the measurement signal and the influence of concentration variations of the internal standard on the measurement signal were shown. Offsets that were adjusted based on the stated theory for the given measurement conditions and material data from the literature were in agreement with the experimentally determined offsets. A measurement comparison with an NDIR reference sensor shows an unexpectedly low bias (<1%) of the non-calibrated sensor response, and comparable statistical uncertainty. PMID:27869656

  16. Resistive Oxygen Gas Sensors for Harsh Environments

    PubMed Central

    Moos, Ralf; Izu, Noriya; Rettig, Frank; Reiß, Sebastian; Shin, Woosuck; Matsubara, Ichiro

    2011-01-01

    Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations. PMID:22163805

  17. Multifunctional potentiometric gas sensor array with an integrated temperature control and temperature sensors

    DOEpatents

    Blackburn, Bryan M; Wachsman, Eric D

    2015-05-12

    Embodiments of the subject invention relate to a gas sensor and method for sensing one or more gases. An embodiment incorporates an array of sensing electrodes maintained at similar or different temperatures, such that the sensitivity and species selectivity of the device can be fine tuned between different pairs of sensing electrodes. A specific embodiment pertains to a gas sensor array for monitoring combustion exhausts and/or chemical reaction byproducts. An embodiment of the subject device related to this invention operates at high temperatures and can withstand harsh chemical environments. Embodiments of the device are made on a single substrate. The devices can also be made on individual substrates and monitored individually as if they were part of an array on a single substrate. The device can incorporate sensing electrodes in the same environment, which allows the electrodes to be coplanar and, thus, keep manufacturing costs low. Embodiments of the device can provide improvements to sensitivity, selectivity, and signal interference via surface temperature control.

  18. Validation of sensor for postoperative positioning with intraocular gas

    PubMed Central

    Brodie, Frank L; Woo, Kelly Y; Balakrishna, Ashwin; Choo, Hyuck; Grubbs, Robert H

    2016-01-01

    Purpose Surgical repair of retinal attachment or macular hole frequently requires intraocular gas. This necessitates specific postoperative positioning to improve outcomes and avoid complications. However, patients struggle with correct positioning. We have developed a novel sensor to detect the position of the gas bubble in the eye and provide feedback to patients in real time. In this paper, we determine the specificity and sensitivity of our sensor in vitro using a model eye. Methods We assessed the reliability of our sensor to detect when a gas bubble has deviated off a model retinal break in a model eye. Various bubble sizes representing the intraocular kinetics of sulfur hexafluoride gas and varying degrees of deviation from the correct position were tested using the sensor attached to a mannequin head with a model eye. Results We recorded 36 data points. The sensor acted appropriately in 33 (91.7%) of them. The sensor triggered the alarm every time the bubble deviated off the break (n=15, sensitivity =100%). However, it triggered the alarm (falsely) 3/21 times when the bubble was correctly positioned over the retinal break (specificity =86%). Conclusion Our device shows excellent sensitivity (100%) and specificity (86%) in detecting whether intraocular gas is tamponading a retinal break in a model eye. PMID:27307698

  19. Compact Laser Multi-gas Spectral Sensors for Spacecraft Systems

    NASA Technical Reports Server (NTRS)

    Tittel, Frank K.

    1997-01-01

    The objective of this research effort has been the development of a new gas sensor technology to meet NASA requirements for spacecraft and space station human life support systems for sensitive selective and real time detection of trace gas species in the mid-infrared spectral region.

  20. Portable Neutron Sensors for Emergency Response Operations

    SciTech Connect

    ,

    2012-06-24

    This article presents the experimental work performed in the area of neutron detector development at the Remote Sensing Laboratory–Andrews Operations (RSL-AO) sponsored by the U.S. Department of Energy, National Nuclear Security Administration (NNSA) in the last four years. During the 1950s neutron detectors were developed mostly to characterize nuclear reactors where the neutron flux is high. Due to the indirect nature of neutron detection via interaction with other particles, neutron counting and neutron energy measurements have never been as precise as gamma-ray counting measurements and gamma-ray spectroscopy. This indirect nature is intrinsic to all neutron measurement endeavors (except perhaps for neutron spin-related experiments, viz. neutron spin-echo measurements where one obtains μeV energy resolution). In emergency response situations generally the count rates are low, and neutrons may be scattered around in inhomogeneous intervening materials. It is also true that neutron sensors are most efficient for the lowest energy neutrons, so it is not as easy to detect and count energetic neutrons. Most of the emergency response neutron detectors are offshoots of nuclear device diagnostics tools and special nuclear materials characterization equipment, because that is what is available commercially. These instruments mostly are laboratory equipment, and not field-deployable gear suited for mobile teams. Our goal is to design and prototype field-deployable, ruggedized, lightweight, efficient neutron detectors.

  1. Gas cell based on cascaded GRIN lens for optical fiber gas sensor

    NASA Astrophysics Data System (ADS)

    Sa, Jiming; Chen, Youping; Zhang, Gang; Zhou, Zude; Cui, Lujun

    2007-12-01

    Based on the theory of gas molecular absorption spectrum, a transmission type gas cell based on cascaded GRIN lens has been designed. The gas cell is the kernel of the optical fiber gas sensor system. The system performance is relative to rationality of gas cell structure. By using GRIN lens couple in gas cell, we can solve the problems of optical discrete components. We use GRIN lens with pigtail fiber as collimating or focusing lens for transmission type of gas cell. To shorten sensor's size and length, and enhance sensor's sensitivity, we present a method by using cascaded GRIN Lens couples to compose a gas cell. With this method, the optical path length is increased and the detection sensitivity of the gas cell is greatly increased. This transmission type of gas cell based on cascaded GRIN lens couples have been applied to our system of absorption spectrum optical fiber gas sensors. We designed and manufactured a gas cell with cascaded GRIN lens couples. Experimental results show that transmission gas cell based on cascaded GRIN lens couples has a good detecting effect.

  2. Volatile organic compound gas sensor based on aluminum-doped zinc oxide with nanoparticle.

    PubMed

    Choi, Nak-Jin; Lee, Hyung-Kun; Moon, Seung Eon; Yang, Woo Seok; Kim, Jongdae

    2013-08-01

    Thick film semiconductor gas sensors based on aluminum-doped zinc oxide (AZO) with nanoparticle size were fabricated to detect volatile organic compound (VOC) existed in building, especially, formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. The sensing materials for screen printing were prepared using roll milling process with binder. The crystallite sizes of prepared materials were about 15 nm through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Gas response characteristics were examined for formaldehyde (HCHO), benzene, carbon monoxide, carbon dioxide gas existing in building. In particular, the sensors showed responses to HCHO gas at sub ppm as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repeativity, selectivity, and response time of sensor. The transients were very sharp, taking less than 2 s for 90% response. The sensor has shown very stable response at 350 degrees C and followed a very good behavior and showed 60% response in 50 ppb HCHO concentration at 350 degrees C operating temperatures.

  3. Digital Architecture for a Trace Gas Sensor Platform

    NASA Technical Reports Server (NTRS)

    Gonzales, Paula; Casias, Miguel; Vakhtin, Andrei; Pilgrim, Jeffrey

    2012-01-01

    A digital architecture has been implemented for a trace gas sensor platform, as a companion to standard analog control electronics, which accommodates optical absorption whose fractional absorbance equivalent would result in excess error if assumed to be linear. In cases where the absorption (1-transmission) is not equivalent to the fractional absorbance within a few percent error, it is necessary to accommodate the actual measured absorption while reporting the measured concentration of a target analyte with reasonable accuracy. This requires incorporation of programmable intelligence into the sensor platform so that flexible interpretation of the acquired data may be accomplished. Several different digital component architectures were tested and implemented. Commercial off-the-shelf digital electronics including data acquisition cards (DAQs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), and microcontrollers have been used to achieve the desired outcome. The most completely integrated architecture achieved during the project used the CPLD along with a microcontroller. The CPLD provides the initial digital demodulation of the raw sensor signal, and then communicates over a parallel communications interface with a microcontroller. The microcontroller analyzes the digital signal from the CPLD, and applies a non-linear correction obtained through extensive data analysis at the various relevant EVA operating pressures. The microcontroller then presents the quantitatively accurate carbon dioxide partial pressure regardless of optical density. This technique could extend the linear dynamic range of typical absorption spectrometers, particularly those whose low end noise equivalent absorbance is below one-part-in-100,000. In the EVA application, it allows introduction of a path-length-enhancing architecture whose optical interference effects are well understood and quantified without sacrificing the dynamic range that allows

  4. Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors.

    PubMed

    Çakır, M Cihan; Çalışkan, Deniz; Bütün, Bayram; Özbay, Ekmel

    2016-09-29

    Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption-dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively.

  5. Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors

    PubMed Central

    Çakır, M. Cihan; Çalışkan, Deniz; Bütün, Bayram; Özbay, Ekmel

    2016-01-01

    Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption–dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively. PMID:27690048

  6. Gas sensors based on semiconducting nanowire field-effect transistors.

    PubMed

    Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

    2014-09-17

    One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed.

  7. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    PubMed Central

    Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

    2014-01-01

    One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed. PMID:25232915

  8. Hydrogen and Oxygen Gas Monitoring System Design and Operation

    SciTech Connect

    Lee C. Cadwallader; Kevin G. DeWall; J. Stephen Herring

    2007-06-01

    This paper describes pertinent design practices of selecting types of monitors, monitor unit placement, setpoint selection, and maintenance considerations for gas monitors. While hydrogen gas monitors and enriched oxygen atmosphere monitors as they would be needed for hydrogen production experiments are the primary focus of this paper, monitors for carbon monoxide and carbon dioxide are also discussed. The experiences of designing, installing, and calibrating gas monitors for a laboratory where experiments in support of the DOE Nuclear Hydrogen Initiative (NHI) are described along with codes, standards, and regulations for these monitors. Information from the literature about best operating practices is also presented. The NHI program has two types of activities. The first, near-term activity is laboratory and pilot-plant experimentation with different processes in the kilogram per day scale to select the most promising types of processes for future applications of hydrogen production. Prudent design calls for indoor gas monitors to sense any hydrogen leaks within these laboratory rooms. The second, longer-term activity is the prototype, or large-scale plants to produce tons of hydrogen per day. These large, outdoor production plants will require area (or “fencepost”) monitoring of hydrogen gas leaks. Some processes will have oxygen production with hydrogen production, and any oxygen releases are also safety concerns since oxygen gas is the strongest oxidizer. Monitoring of these gases is important for personnel safety of both indoor and outdoor experiments. There is some guidance available about proper placement of monitors. The fixed point, stationary monitor can only function if the intruding gas contacts the monitor. Therefore, monitor placement is vital to proper monitoring of the room or area. Factors in sensor location selection include: indoor or outdoor site, the location and nature of potential vapor/gas sources, chemical and physical data of the

  9. Fault Diagnosis for Micro-Gas Turbine Engine Sensors via Wavelet Entropy

    PubMed Central

    Yu, Bing; Liu, Dongdong; Zhang, Tianhong

    2011-01-01

    Sensor fault diagnosis is necessary to ensure the normal operation of a gas turbine system. However, the existing methods require too many resources and this need can’t be satisfied in some occasions. Since the sensor readings are directly affected by sensor state, sensor fault diagnosis can be performed by extracting features of the measured signals. This paper proposes a novel fault diagnosis method for sensors based on wavelet entropy. Based on the wavelet theory, wavelet decomposition is utilized to decompose the signal in different scales. Then the instantaneous wavelet energy entropy (IWEE) and instantaneous wavelet singular entropy (IWSE) are defined based on the previous wavelet entropy theory. Subsequently, a fault diagnosis method for gas turbine sensors is proposed based on the results of a numerically simulated example. Then, experiments on this method are carried out on a real micro gas turbine engine. In the experiment, four types of faults with different magnitudes are presented. The experimental results show that the proposed method for sensor fault diagnosis is efficient. PMID:22163734

  10. Fault diagnosis for micro-gas turbine engine sensors via wavelet entropy.

    PubMed

    Yu, Bing; Liu, Dongdong; Zhang, Tianhong

    2011-01-01

    Sensor fault diagnosis is necessary to ensure the normal operation of a gas turbine system. However, the existing methods require too many resources and this need can't be satisfied in some occasions. Since the sensor readings are directly affected by sensor state, sensor fault diagnosis can be performed by extracting features of the measured signals. This paper proposes a novel fault diagnosis method for sensors based on wavelet entropy. Based on the wavelet theory, wavelet decomposition is utilized to decompose the signal in different scales. Then the instantaneous wavelet energy entropy (IWEE) and instantaneous wavelet singular entropy (IWSE) are defined based on the previous wavelet entropy theory. Subsequently, a fault diagnosis method for gas turbine sensors is proposed based on the results of a numerically simulated example. Then, experiments on this method are carried out on a real micro gas turbine engine. In the experiment, four types of faults with different magnitudes are presented. The experimental results show that the proposed method for sensor fault diagnosis is efficient.

  11. Extraction and evaluation of gas-flow-dependent features from dynamic measurements of gas sensors array

    NASA Astrophysics Data System (ADS)

    Kalinowski, Paweł; Woźniak, Łukasz; Jasiński, Grzegorz; Jasiński, Piotr

    2016-11-01

    Gas analyzers based on gas sensors are the devices which enable recognition of various kinds of volatile compounds. They have continuously been developed and investigated for over three decades, however there are still limitations which slow down the implementation of those devices in many applications. For example, the main drawbacks are the lack of selectivity, sensitivity and long term stability of those devices caused by the drift of utilized sensors. This implies the necessity of investigations not only in the field of development of gas sensors construction, but also the development of measurement procedures or methods of analysis of sensor responses which compensate the limitations of sensors devices. One of the fields of investigations covers the dynamic measurements of sensors or sensor-arrays response with the utilization of flow modulation techniques. Different gas delivery patterns enable the possibility of extraction of unique features which improves the stability and selectivity of gas detecting systems. In this article three utilized flow modulation techniques are presented, together with the proposition of the evaluation method of their usefulness and robustness in environmental pollutants detecting systems. The results of dynamic measurements of an commercially available TGS sensor array in the presence of nitrogen dioxide and ammonia are shown.

  12. The significance of gas for offshore operations

    NASA Astrophysics Data System (ADS)

    Sills, G. C.; Wheeler, S. J.

    1992-10-01

    The purpose of this paper is to present an overview of the physical behaviour of a seabed containing undissolved gas in the light of laboratory simulations undertaken at Oxford, Belfast and Sheffield Universities. This physical behaviour is significant for offshore operations in several ways. Gas may exist in high pressure pockets, trapped beneath low permeability clays, which form a blow out hazard during drilling. In fine-grained soils, it exists in voids distributed through the soil, at pressures only a little greater than te ambient water pressure. In this condition, it is unlikely to induced casastrophic failure, but will affect the foundation behaviour through changes in compressibility and strength. In sands, gas may be present in pores between particles, replacing water but not affecting the soil structure. There are common features in all these cases, in that the gas-water interaction occurs through surface tension, acting in menisci whose curvature is affected by the soil particle sizes, shapes and packing. These menisci determine the differences between gas and water pressure that may exist in the soil. Results are presented to show that the compressibility and undrained shear strength of a fine-grained soil are reduced by the presence of gas in a predictable manner, with a similar conclusion for the undrained strength of a gassy sand.

  13. Methanol sensor operated in a passive mode

    DOEpatents

    Ren, Xiaoming; Gottesfeld, Shimshon

    2002-01-01

    A sensor outputs a signal related to a concentration of methanol in an aqueous solution adjacent the sensor. A membrane electrode assembly (MEA) is included with an anode side and a cathode side. An anode current collector supports the anode side of the MEA and has a flow channel therethrough for flowing a stream of the aqueous solution and forms a physical barrier to control access of the methanol to the anode side of the MEA. A cathode current collector supports the cathode side of the MEA and is configured for air access to the cathode side of the MEA. A current sensor is connected to measure the current in a short circuit across the sensor electrodes to provide an output signal functionally related to the concentration of methanol in the aqueous solution.

  14. Nanocomposite based flexible ultrasensitive resistive gas sensor for chemical reactions studies

    PubMed Central

    Pandey, Sadanand; Goswami, Gopal K.; Nanda, Karuna K.

    2013-01-01

    Room temperature operation, low detection limit and fast response time are highly desirable for a wide range of gas sensing applications. However, the available gas sensors suffer mainly from high temperature operation or external stimulation for response/recovery. Here, we report an ultrasensitive-flexible-silver-nanoparticle based nanocomposite resistive sensor for ammonia detection and established the sensing mechanism. We show that the nanocomposite can detect ammonia as low as 500 parts-per-trillion at room temperature in a minute time. Furthermore, the evolution of ammonia from different chemical reactions has been demonstrated using the nanocomposite sensor as an example. Our results demonstrate the proof-of-concept for the new detector to be used in several applications including homeland security, environmental pollution and leak detection in research laboratories and many others. PMID:23803772

  15. Miniaturized ionization gas sensors from single metal oxide nanowires.

    PubMed

    Hernandez-Ramirez, Francisco; Prades, Juan Daniel; Hackner, Angelika; Fischer, Thomas; Mueller, Gerhard; Mathur, Sanjay; Morante, Joan Ramon

    2011-02-01

    Gas detection experiments were performed with individual tin dioxide (SnO2) nanowires specifically configured to observe surface ion (SI) emission response towards representative analyte species. These devices were found to work at much lower temperatures (T≈280 °C) and bias voltages (V≈2 V) than their micro-counterparts, thereby demonstrating the inherent potential of individual nanostructures in building functional nanodevices. High selectivity of our miniaturized sensors emerges from the dissimilar sensing mechanisms of those typical of standard resistive-type sensors (RES). Therefore, by employing this detection principle (SI) together with RES measurements, better selectivity than that observed in standard metal oxide sensors could be demonstrated. Simplicity and specificity of the gas detection as well as low-power consumption make these single nanowire devices promising technological alternatives to overcome the major drawbacks of solid-state sensor technologies.

  16. RSTA sensor integration onto PackBot for urban operations

    NASA Astrophysics Data System (ADS)

    Young, Stuart H.; Martin, Patrick

    2004-09-01

    As the Army transforms to the Objective Force, particular attention must be paid to operations in Complex and Urban Terrain. Because our adversaries realize that we don"t have battlefield dominance in the urban environment, and because population growth and migration to urban environments is still on the increase, our adversaries will continue to draw us into operations in the urban environment. The Army Research Laboratory (ARL) is developing technology to equip our soldiers for the urban operations of the future. Sophisticated small robotic platforms with diverse sensor suites will be an integral part of the Future Force, and must be able to collaborate not only amongst themselves but also with their manned partners. The Army Research Laboratory has developed a Reconnaissance, Surveillance, and Target Acquisition (RSTA) sensor payload for integration onto an iRobot Packbot. The RSTA sensor payload is equipped with an acoustic array that will detect and localize on an impulsive noise event, such as a sniper's weapon firing. Additionally, the robot sensor head is equipped with visible and thermal camera for operations both day and night. The RSTA sensor head equipped Packbot can then be deployed by dismounted soldiers to enhance their situational awareness in the urban environment. The information from one Packbot can then be fused with other sensors as part of a sensor network. Sensor equipped Packbots provides an awesome capability to the future dismounted infantry soldier during warfighting and peacekeeping operations in complex and urban terrain by enhancing their situational awareness and improving their survivability.

  17. Simulating Operation of a Complex Sensor Network

    NASA Technical Reports Server (NTRS)

    Jennings, Esther; Clare, Loren; Woo, Simon

    2008-01-01

    Simulation Tool for ASCTA Microsensor Network Architecture (STAMiNA) ["ASCTA" denotes the Advanced Sensors Collaborative Technology Alliance.] is a computer program for evaluating conceptual sensor networks deployed over terrain to provide military situational awareness. This or a similar program is needed because of the complexity of interactions among such diverse phenomena as sensing and communication portions of a network, deployment of sensor nodes, effects of terrain, data-fusion algorithms, and threat characteristics. STAMiNA is built upon a commercial network-simulator engine, with extensions to include both sensing and communication models in a discrete-event simulation environment. Users can define (1) a mission environment, including terrain features; (2) objects to be sensed; (3) placements and modalities of sensors, abilities of sensors to sense objects of various types, and sensor false alarm rates; (4) trajectories of threatening objects; (5) means of dissemination and fusion of data; and (6) various network configurations. By use of STAMiNA, one can simulate detection of targets through sensing, dissemination of information by various wireless communication subsystems under various scenarios, and fusion of information, incorporating such metrics as target-detection probabilities, false-alarm rates, and communication loads, and capturing effects of terrain and threat.

  18. Design Of A Sorbent/desorbent Unit For Sample Pre-treatment Optimized For QMB Gas Sensors

    SciTech Connect

    Pennazza, G.; Cristina, S.; Santonico, M.; Martinelli, E.; Di Natale, C.; D'Amico, A.; Paolesse, R.

    2009-05-23

    Sample pre-treatment is a typical procedure in analytical chemistry aimed at improving the performance of analytical systems. In case of gas sensors sample pre-treatment systems are devised to overcome sensors limitations in terms of selectivity and sensitivity. For this purpose, systems based on adsorption and desorption processes driven by temperature conditioning have been illustrated. The involvement of large temperature ranges may pose problems when QMB gas sensors are used. In this work a study of such influences on the overall sensing properties of QMB sensors are illustrated. The results allowed the design of a pre-treatment unit coupled with a QMB gas sensors array optimized to operate in a suitable temperatures range. The performance of the system are illustrated by the partially separation of water vapor in a gas mixture, and by substantial improvement of the signal to noise ratio.

  19. Composed planar Hall effect sensors with dual-mode operation

    NASA Astrophysics Data System (ADS)

    Mor, Vladislav; Roy, Debangsu; Schultz, Moty; Klein, Lior

    2016-02-01

    We present a composed planar Hall effect sensor with two modes of operation: (a) an ON mode where the composed sensor responds to magnetic field excitations similarly to the response of a regular planar Hall effect sensor, and (b) an OFF mode where the response is negligible. The composed planar Hall effect sensor switches from the OFF mode to the ON mode when it is exposed to a magnetic field which exceeds a certain threshold determined by the sensor design. The features of this sensor make it useful as a switch triggered by magnetic field and as a sensing device with memory, as its mode of operation indicates exposure to a magnetic field larger than a certain threshold without the need to be activated during the exposure itself.

  20. Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays

    PubMed Central

    Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

    2012-01-01

    This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals. PMID:23443378

  1. Negative admittance in resistive metal oxide gas sensors

    NASA Astrophysics Data System (ADS)

    Varpula, A.; Novikov, S.; Sinkkonen, J.; Utriainen, M.

    2008-03-01

    The negative admittance effect is observed in a WO3-based resistive gas sensor MOS1 from Environics Oy. The effect is caused by electron trapping (i.e. oxygen ionization) at the grain boundary. The results show that the current component related to the modulation of the grain-boundary barrier dominates in dry clean air and the charging or discharging current dominates in humid air conditions. An equivalent electrical circuit model for the sensor response is presented.

  2. Electrospray-printed nanostructured graphene oxide gas sensors.

    PubMed

    Taylor, Anthony P; Velásquez-García, Luis F

    2015-12-18

    We report low-cost conductometric gas sensors that use an ultrathin film made of graphene oxide (GO) nanoflakes as transducing element. The devices were fabricated by lift-off metallization and near-room temperature, atmospheric pressure electrospray printing using a shadow mask. The sensors are sensitive to reactive gases at room temperature without requiring any post heat treatment, harsh chemical reduction, or doping with metal nanoparticles. The sensors' response to humidity at atmospheric pressure tracks that of a commercial sensor, and is linear with changes in humidity in the 10%-60% relative humidity range while consuming <6 μW. Devices with GO layers printed by different deposition recipes yielded nearly identical response characteristics, suggesting that intrinsic properties of the film control the sensing mechanism. The gas sensors successfully detected ammonia at concentrations down to 500 ppm (absolute partial pressure of ∼5 × 10(-4) T) at ∼1 T pressure, room temperature conditions. The sensor technology can be used in a great variety of applications including air conditioning and sensing of reactive gas species in vacuum lines and abatement systems.

  3. Illicit material detector based on gas sensors and neural networks

    NASA Astrophysics Data System (ADS)

    Grimaldi, Vincent; Politano, Jean-Luc

    1997-02-01

    In accordance with its missions, le Centre de Recherches et d'Etudes de la Logistique de la Police Nationale francaise (CREL) has been conducting research for the past few years targeted at detecting drugs and explosives. We have focused our approach of the underlying physical and chemical detection principles on solid state gas sensors, in the hope of developing a hand-held drugs and explosives detector. The CREL and Laboratory and Scientific Services Directorate are research partners for this project. Using generic hydrocarbon, industrially available, metal oxide sensors as illicit material detectors, requires usage precautions. Indeed, neither the product's concentrations, nor even the products themselves, belong to the intended usage specifications. Therefore, the CREL is currently investigating two major research topics: controlling the sensor's environment: with environmental control we improve the detection of small product concentration; determining detection thresholds: both drugs and explosives disseminate low gas concentration. We are attempting to quantify the minimal concentration which triggers detection. In the long run, we foresee a computer-based tool likely to detect a target gas in a noisy atmosphere. A neural network is the suitable tool for interpreting the response of heterogeneous sensor matrix. This information processing structure, alongside with proper sensor environment control, will lessen the repercussions of common MOS sensor sensitivity characteristic dispersion.

  4. Novel SH-SAW gas sensor based on graphene

    NASA Astrophysics Data System (ADS)

    Nikolaou, I.; Hallil, H.; Deligeorgis, G.; Conedera, V.; Garcia, H.; Dejous, C.; Rebière, D.

    2015-05-01

    In this article, a novel gas sensor platform has been studied. Several layers of graphene have been deposited on a SH-SAW, as a sensitive layer. Innovative methods of graphene solutions have been prepared in order to explore gas sensing applications. The real time detection measurement of the coated sensor under ethanol and humidity is presented. The adsorption of vapors leads to a frequency shift of 10.5 kHz and 22.7 kHz, at exposure of 100 ppm of ethanol and 6.22% of Relative Humidity, respectively. The experiments have been realized at room temperature; rapid response and recovery time were observed.

  5. Design of micro-sensor-array detector for toxic gas

    NASA Astrophysics Data System (ADS)

    Liao, Hai-yang; Tian, Peng

    2010-08-01

    To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is based on the principle that gas sensors will show different colors after reaction with the toxic gas. The tricolor information about the concentration of gas is collected by the color liner CCD. A control handling system with C8051F021 MCU as the core is implemented and embedded into the detector to perform the functions of gas sampling, data collection and analysis calculation. Data acquisition experimental results show that the proposed scheme can effectively collect the color information after gas reaction. Moreover, the system has many important advantages, such as small size, compact structure, high degree of automation, fast detection speed and high performance-cost ratio, etc.

  6. Electrodes for solid state gas sensor

    DOEpatents

    Mukundan, Rangachary; Brosha, Eric L.; Garzon, Fernando

    2007-05-08

    A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

  7. Electrodes for solid state gas sensor

    DOEpatents

    Mukundan, Rangachary; Brosha, Eric L.; Garzon, Fernando

    2003-08-12

    A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

  8. ZnO Coated Nanospring-Based Gas Sensors

    NASA Astrophysics Data System (ADS)

    Bakharev, Pavel Viktorovich

    The current research demonstrates new techniques for characterization of electrical transport properties of the metal oxide polycrystalline structures, gas and vapor phase kinetics, surface processes such as gas-surface, vapor-surface interactions and redox processes by applying novel gas sensing devices. Real-time sensor electrical response characteristics obtained under highly controlled laboratory conditions have been used to characterize corresponding surface interactions and electrical properties of the gas sensitive structures. Novel redox chemical sensors (chemiresistors) have been fabricated with 3-D and 1-D ZnO coated nanospring (NS) structures. Silica NSs served as insulating scaffolding for a ZnO gas sensitive layer and has been grown via a vapor-liquid-solid (VLS) mechanism by using a chemical vapor deposition (CVD) technique. The NSs have been coated with polycrystalline ZnO by atomic layer deposition (ALD). The chemiresistor devices have been thoroughly characterized in terms of their crystal structures (by XRD, FESEM, TEM, and ellipsometry) and their electrical response properties. A 3-D gas sensor has been constructed from a xenon light bulb by coating it with a 3-D zinc oxide coated silica nanospring mat, where the xenon light bulb served as a sensor heater. This inexpensive sensor platform has been used to characterize gas-solid, vapor-solid, and redox processes. The optimal temperature of the gas sensitive ZnO layer, the temperature of the vapor-gas mixture and the crystal structure of the gas sensitive layer have been determined to reach the highest sensitivity of the gas sensors. The activation energy of toluene oxidation (Ed) on the ZnO surface and the activation energy of oxidation (Ea) of the depleted ZnO surface have been determined and analyzed. A 1-D chemiresistor has been fabricated with a single ZnO coated silica nanospring by photolithography. The question of sensor sensitivity of MOS nanomaterials and MOS thin films has been addressed

  9. Opportunities of Wireless Sensors and Controls for Building Operation

    SciTech Connect

    Kintner-Meyer, Michael CW

    2004-09-30

    This paper characterizes commercially available wireless technologies that are suitable for use in commercial buildings. It describes two demonstration projects of wireless sensors and their integration into existing control networks, and discusses their cost per sensor, their ease of installation, and their reliability. The author will discuss the operational and energy benefits of the wireless sensors and report on the energy and cost savings estimates. The paper will conclude with some practical considerations for the installation of wireless sensors and provide a future outlook for wireless technologies in buildings applications.

  10. Continued Optical Sensor Operations in a Laser Environment

    DTIC Science & Technology

    2012-10-01

    Power (W) Aperture (mm) Intensity at target (W/m2) Gain of laser to desired signal handheld 532 0.5 1.5 1120 @ 25 km 5.6 × 1024 Industrial diode ...AIR UNIVERSITY AIR WAR COLLEGE Continued Optical Sensor Operations in a Laser Environment WILLIAM J. DIEHL Commander, USN...COVERED 00-00-2012 to 00-00-2012 4. TITLE AND SUBTITLE Continued Optical Sensor Operations in a Laser Environment 5a. CONTRACT NUMBER 5b. GRANT

  11. Wearable, wireless gas sensors using highly stretchable and transparent structures of nanowires and graphene

    NASA Astrophysics Data System (ADS)

    Park, Jihun; Kim, Joohee; Kim, Kukjoo; Kim, So-Yun; Cheong, Woon Hyung; Park, Kyeongmin; Song, Joo Hyeb; Namgoong, Gyeongho; Kim, Jae Joon; Heo, Jaeyeong; Bien, Franklin; Park, Jang-Ung

    2016-05-01

    Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area.Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the `Internet of Things' area. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01468b

  12. Multiwalled carbon nanotubes-zinc oxide nanocomposites as low temperature toluene gas sensor

    NASA Astrophysics Data System (ADS)

    Septiani, Ni Luh Wulan; Yuliarto, Brian; Nugraha; Dipojono, Hermawan Kresno

    2017-03-01

    The performance of nanocomposite MWCNT-ZnO thin films was investigated as toluene gas sensor. The nanocomposites MWCNT-ZnO thin films were synthesized by reflux method with the variation of MWCNT:ZnO ratio on 1:0, 3:1, 1:1, 1:3, and 0:1. Crystallinity and morphology characterization show that the crystal structure was not influenced by the presence of MWCNT, and the presence of MWCNTs could prevent the agglomeration of ZnO nanostructure. The dynamic response curve of nanocomposites MWCNT-ZnO thin films shows two different patterns at low temperature region and high temperature region. At low temperature region, the sensor response decreases as the increasing operating temperature and increasing the concentration of ZnO. On the other hand, at high temperature region, the sensor response increases as the increasing operating temperature and increasing the concentration of ZnO. Moreover, the variation concentration of MWCNT and ZnO can decrease the operating temperature of the sensors. The sensor with the ratio of MWCNT:ZnO at 1:3 show highest sensor response that reaches 17% at 150 °C of operating temperature, while the pure MWCNTs and pure ZnO show no response at that temperature.

  13. Specific and reproducible gas sensors utilizing gas-phase chemical reaction on organic transistors.

    PubMed

    Zang, Yaping; Zhang, Fengjiao; Huang, Dazhen; Di, Chong-an; Meng, Qing; Gao, Xike; Zhu, Daoben

    2014-05-01

    Utilizing a textbook reaction on the surface of an organic active channel, achieves sensitive detection of HCl, NH3 and NO2, with good selectivity, excellent reproducibility, and satisfactory stability. These results reveal gas-phase reaction assisted detection as a unique and promising approach to construct practical applicable gas sensors with typical organic transistors.

  14. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    PubMed Central

    Gu, Haoshuang; Wang, Zhao; Hu, Yongming

    2012-01-01

    Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

  15. Harmful Gas Recognition Exploiting a CTL Sensor Array

    PubMed Central

    Wang, Qihui; Xie, Lijun; Zhu, Bo; Zheng, Yao; Cao, Shihua

    2013-01-01

    In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field. PMID:24113681

  16. Chemical discrimination in turbulent gas mixtures with MOX sensors validated by gas chromatography-mass spectrometry.

    PubMed

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

    2014-10-16

    Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance.

  17. Novel carbon dioxide gas sensor based on infrared absorption

    NASA Astrophysics Data System (ADS)

    Zhang, Guangjun; Lui, Junfang; Yuan, Mei

    2000-08-01

    The feasibility of sensing carbon dioxide with a IR single- beam optical structure is studied, and a novel carbon dioxide gas sensor based on IR absorption is achieved. Applying the Lambert-Beer law and some key techniques such as current stabilization for IR source, using a high-quality IR detector, and data compensation for the influences of ambience temperature and atmosphere total pressure, the sensor can measure carbon dioxide with high precision and efficiency. The mathematical models for providing temperature and pressure compensation for the sensor are established. Moreover the solutions to the models are proposed. Both the models and the solutions to the models are verified via experiments. The sensor possesses the advantages of small volume, light weight, low power consumption, and high reliability. Therefore it can be used in many associated fields, such as environmental protection, processing control, chemical analysis, medical diagnosis, and space environmental and control systems.

  18. Ferroelectric Dispersed Composite Solid Electrolyte for CO2 Gas Sensor

    NASA Astrophysics Data System (ADS)

    Singh, K.; Ambekar, P.; Bhoga, S. S.

    2002-12-01

    The Li2CO3:LiNbO3 composite system was investigated for the application in electrochemical gas sensor. The conductivity maximum is observed for 50Li2CO3+50LiNbO3. An enhancement in conductivity is understood to be due to the percolation threshold. The composite is also seen less sensitive to moisture. Potentiometric sensors are obtained using optimized composition. At the reference electrode, the activity of Li+ is fixed by using open reference electrode material. Good reversibility of cell emf was observed for PCO2 ranging from 200 ppm to 20% at 400°C. The cell response was Nernstian, following nearly two-electron reaction. The sensor showed negligible cross-sensitivity to moisture. Developed solid electrolyte not only exhibit shorter response time but also improves over all performance relative to the sensor based on pure carbonate.

  19. Data set from gas sensor array under flow modulation.

    PubMed

    Ziyatdinov, Andrey; Fonollosa, Jordi; Fernández, Luis; Gutiérrez-Gálvez, Agustín; Marco, Santiago; Perera, Alexandre

    2015-06-01

    Recent studies in neuroscience suggest that sniffing, namely sampling odors actively, plays an important role in olfactory system, especially in certain scenarios such as novel odorant detection. While the computational advantages of high frequency sampling have not been yet elucidated, here, in order to motivate further investigation in active sampling strategies, we share the data from an artificial olfactory system made of 16 MOX gas sensors under gas flow modulation. The data were acquired on a custom set up featured by an external mechanical ventilator that emulates the biological respiration cycle. 58 samples were recorded in response to a relatively broad set of 12 gas classes, defined from different binary mixtures of acetone and ethanol in air. The acquired time series show two dominant frequency bands: the low-frequency signal corresponds to a conventional response curve of a sensor in response to a gas pulse, and the high-frequency signal has a clear principal harmonic at the respiration frequency. The data are related to the study in [1], and the data analysis results reported there should be considered as a reference point. The data presented here have been deposited to the web site of The University of California at Irvine (UCI) Machine Learning Repository (https://archive.ics.uci.edu/ml/datasets/Gas+sensor+array+under+flow+modulation). The code repository for reproducible analysis applied to the data is hosted at the GutHub web site (https://github.com/variani/pulmon). The data and code can be used upon citation of [1].

  20. Functionalised zinc oxide nanowire gas sensors: Enhanced NO(2) gas sensor response by chemical modification of nanowire surfaces.

    PubMed

    Waclawik, Eric R; Chang, Jin; Ponzoni, Andrea; Concina, Isabella; Zappa, Dario; Comini, Elisabetta; Motta, Nunzio; Faglia, Guido; Sberveglieri, Giorgio

    2012-01-01

    Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO(2) produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO(2) down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO(2) compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ΔR/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO(2) target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.

  1. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns

    PubMed Central

    Itoh, Toshio; Miwa, Toshio; Tsuruta, Akihiro; Akamatsu, Takafumi; Izu, Noriya; Shin, Woosuck; Park, Jangchul; Hida, Toyoaki; Eda, Takeshi; Setoguchi, Yasuhiro

    2016-01-01

    Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis. PMID:27834896

  2. Development of an Exhaled Breath Monitoring System with Semiconductive Gas Sensors, a Gas Condenser Unit, and Gas Chromatograph Columns.

    PubMed

    Itoh, Toshio; Miwa, Toshio; Tsuruta, Akihiro; Akamatsu, Takafumi; Izu, Noriya; Shin, Woosuck; Park, Jangchul; Hida, Toyoaki; Eda, Takeshi; Setoguchi, Yasuhiro

    2016-11-10

    Various volatile organic compounds (VOCs) in breath exhaled by patients with lung cancer, healthy controls, and patients with lung cancer who underwent surgery for resection of cancer were analyzed by gas condenser-equipped gas chromatography-mass spectrometry (GC/MS) for development of an exhaled breath monitoring prototype system involving metal oxide gas sensors, a gas condenser, and gas chromatography columns. The gas condenser-GC/MS analysis identified concentrations of 56 VOCs in the breath exhaled by the test population of 136 volunteers (107 patients with lung cancer and 29 controls), and selected four target VOCs, nonanal, acetoin, acetic acid, and propanoic acid, for use with the condenser, GC, and sensor-type prototype system. The prototype system analyzed exhaled breath samples from 101 volunteers (74 patients with lung cancer and 27 controls). The prototype system exhibited a level of performance similar to that of the gas condenser-GC/MS system for breath analysis.

  3. Nanostructured Gas Sensors for Health Care: An Overview

    PubMed Central

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-01-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here. PMID:26491544

  4. Nanostructured Gas Sensors for Health Care: An Overview.

    PubMed

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-07-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here.

  5. A smart microelectromechanical sensor and switch triggered by gas

    NASA Astrophysics Data System (ADS)

    Bouchaala, Adam; Jaber, Nizar; Shekhah, Osama; Chernikova, Valeriya; Eddaoudi, Mohamed; Younis, Mohammad I.

    2016-07-01

    There is an increasing interest to realize smarter sensors and actuators that can deliver a multitude of sophisticated functionalities while being compact in size and of low cost. We report here combining both sensing and actuation on the same device based on a single microstructure. Specifically, we demonstrate a smart resonant gas (mass) sensor, which in addition to being capable of quantifying the amount of absorbed gas, can be autonomously triggered as an electrical switch upon exceeding a preset threshold of absorbed gas. Toward this, an electrostatically actuated polymer microbeam is fabricated and is then functionalized with a metal-organic framework, namely, HKUST-1. The microbeam is demonstrated to absorb vapors up to a certain threshold, after which is shown to collapse through the dynamic pull-in instability. Upon pull-in, the microstructure can be made to act as an electrical switch to achieve desirable actions, such as alarming.

  6. Methods for gas detection using stationary hyperspectral imaging sensors

    DOEpatents

    Conger, James L [San Ramon, CA; Henderson, John R [Castro Valley, CA

    2012-04-24

    According to one embodiment, a method comprises producing a first hyperspectral imaging (HSI) data cube of a location at a first time using data from a HSI sensor; producing a second HSI data cube of the same location at a second time using data from the HSI sensor; subtracting on a pixel-by-pixel basis the second HSI data cube from the first HSI data cube to produce a raw difference cube; calibrating the raw difference cube to produce a calibrated raw difference cube; selecting at least one desired spectral band based on a gas of interest; producing a detection image based on the at least one selected spectral band and the calibrated raw difference cube; examining the detection image to determine presence of the gas of interest; and outputting a result of the examination. Other methods, systems, and computer program products for detecting the presence of a gas are also described.

  7. [Design of non-dispersed infrared (NDIR) methane gas sensor].

    PubMed

    Zhao, Zheng-Jie; Liu, Dong-Xu; Zhang, Ji-Long; Wang, Zhi-Bin; Li, Xiao; Tian, Er-Ming

    2011-02-01

    A non-dispersed infrared (NDIR) methane gas sensors system based on infrared absorption spectrum theory was designed according to single light beam and double wavelengths technology. In the system, an infrared LED IRL715 serving as the light power, a absorptive gas cell with the function of dust-proof and damp-proof and a pyroelectric detector LIM-262 are composed of optical probe. Signal condition uses active filter circuit and differential amplifier, and binomial expression fits the relation curve between methane concentration and voltage, which realizes accurate detection of gas concentration. Experiment approved that the sensor system with good consistency and applicability can detect the range of 5% methane reliably and have 0.5% of the sensitivity, possessing the conditions for industrial applications initially.

  8. Characterization of molecular recognition in gas sensors

    SciTech Connect

    Hierlemann, A.; Ricco, A.J.; Bodenhoefer, K.; Goepel, W.

    1998-08-01

    Molecular recognition is an important topic when searching for new, selective coating materials for chemical sensing. Recently, the general idea of molecular recognition in the gas phase was challenged by Grate et al. However, in earlier thickness-shear mode resonator (TSMR) investigations, convincing evidence was presented for specific recognition of particular analyte target molecules. In this study, the authors systematically investigated coatings previously shown to be highly selective, such as the bucket-like cyclodextrins for chiral recognition, Ni-camphorates for the specific detection of the bases pyridine and DMMP (dimethylmethylphosphonate), and phthalocyanines to specifically detect benzene, toluene, and xylene (BTX).

  9. Sensors control gas metal arc welding

    SciTech Connect

    Siewert, T.A.; Madigan, R.B.; Quinn, T.P.

    1997-04-01

    The response time of a trained welder from the time a weld problem is identified to the time action is taken is about one second--especially after a long, uneventful period of welding. This is acceptable for manual welding because it is close to the time it takes for the weld pool to solidify. If human response time were any slower, manual welding would not be possible. However, human response time is too slow to respond to some weld events, such as melting of the contact tube in gas metal arc welding (GMAW), and only automated intelligent control systems can react fast enough to correct or avoid these problems. Control systems incorporate welding knowledge that enables intelligent decisions to be made about weld quality and, ultimately, to keep welding parameters in the range where only high-quality welds are produced. This article discusses the correlation of electrical signals with contact-tube wear, changes in shielding gas, changes in arc length, and other weld process data.

  10. A comparative study on simulation performances of rigid and bendable SAW for gas sensor

    NASA Astrophysics Data System (ADS)

    Sidek, Fatini; Arsat, Rashidah; Ibrahim, Rafidah; Idris, Aizzat Ayuni Mohad; Johari, Zaharah; Ling, Leow Pei

    2017-03-01

    Flexible Surface Acoustic Wave (SAW) devices are very promising technology for various applications that offers excellent flexibility, low in cost and light weight. In this paper, a SAW gas sensor is designed and simulated using COMSOL Multiphysics to investigate the degree of bending effect on the frequency and displacement. The investigations were conducted onto SAW gas sensor as rigid and two different bends direction; bend-in (concave) and bend-out (convex). The operating frequency of the SAW sensor were found to be at the range of 80-200 MHz. The frequency shift of the sensor were obtained after exposing the polyisobutylene (PIB) to the dichloromethane DCM gas which will change the density of sensing layer. From the simulation, it is shown that resonance frequency range of 189MHz for the rigid substrate with displacement of 0.706 nm. Notably, the bending degree of h range from 0.2 µm to 1.25 µm exhibits reduction for displacement and frequency. The higher frequency of bend-out (convex) design achieve is 1.8945 MHz with displacement of 0.68 nm at curve of h= 0.2 µm, Improvement have been observed for the frequency shift of 14 Hz and sensitivity of 1324.24. It shows that the sensor is more sensitive to detect the gas. The evaluation of device bending effect on the eigenfrequency, displacement and frequency shift provide ways to enhance the sensitivity of the gas sensor and expand its possibility of realizing their benefit particularly for sensing device enhancement.

  11. Method for operating a flue gas desulfurization

    SciTech Connect

    Karger, R.; Weinzierl, K.

    1983-02-01

    A method of operating a flue gas desulfurization with a steam power plant heated with fossil fuels. The sulfur dioxide contained in the flue gas is removed in a wash tower by means of an excess of milk of lime or limestone, and the resulting sulfite is oxidized with air at a low ph-value into calcium sulfate. The non-converted milk of lime or limestone is neutralized at least partially by an addition of acid waste waters from a complete desalination plant for the supply water, and/or by an addition of acid condensate from the flue or chimney of the steam power plant. An installation for carrying out the method of the present invention includes a wash tower having flue gas flowing therethrough, an oxidation tower having air flowing therethrough, milk of lime or limestone supply into the wash tower, and a delivery device for the wash liquid in the wash tower and in the oxidation tower, with the device having a pump for liquid drawn off from the sump of the wash tower. The sump of the wash tower is connected with a supply line for acid waste water from a complete desalination plant, and/or with a supply line for acid condensate from the chimney or flue of the steam power plant.

  12. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  13. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  14. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  15. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  16. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  17. Gas Sensor Evaluations in Polymer Combustion Product Atmospheres

    NASA Technical Reports Server (NTRS)

    Delgado, Rafael H.; Davis, Dennis D.; Beeson, Harold D.

    1999-01-01

    Toxic gases produced by the combustion or thermo-oxidative degradation of materials such as wire insulation, foam, plastics, or electronic circuit boards in space shuttle or space station crew cabins may pose a significant hazard to the flight crew. Toxic gas sensors are routinely evaluated in pure gas standard mixtures, but the possible interferences from polymer combustion products are not routinely evaluated. The NASA White Sands Test Facility (WSTF) has developed a test system that provides atmospheres containing predetermined quantities of target gases combined with the coincidental combustion products of common spacecraft materials. The target gases are quantitated in real time by infrared (IR) spectroscopy and verified by grab samples. The sensor responses are recorded in real time and are compared to the IR and validation analyses. Target gases such as carbon monoxide, hydrogen cyanide, hydrogen chloride, and hydrogen fluoride can be generated by the combustion of poly(vinyl chloride), polyimide-fluoropolymer wire insulation, polyurethane foam, or electronic circuit board materials. The kinetics and product identifications for the combustion of the various materials were determined by thermogravimetric-IR spectroscopic studies. These data were then scaled to provide the required levels of target gases in the sensor evaluation system. Multisensor toxic gas monitors from two manufacturers were evaluated using this system. In general, the sensor responses satisfactorily tracked the real-time concentrations of toxic gases in a dynamic mixture. Interferences from a number of organic combustion products including acetaldehyde and bisphenol-A were minimal. Hydrogen bromide in the products of circuit board combustion registered as hydrogen chloride. The use of actual polymer combustion atmospheres for the evaluation of sensors can provide additional confidence in the reliability of the sensor response.

  18. Optical fiber sensor for temperature measurement from 600 to 1900 C in gas turbine engines

    NASA Technical Reports Server (NTRS)

    Tregay, G. W.; Calabrese, P. R.; Kaplin, P. L.; Finney, M. J.

    1991-01-01

    A temperature sensor system has been fabricated specifically for the harsh environment encountered in temperature measurement on gas turbine engines. Four components comprised the system: a thermally emissive source, a high temperature lightguide, a flexible optical cable and an electro-optic signal processor. The emissive source was located inside a sapphire rod so that the sapphire serves as both a lightguide and as a protective shroud. As the probe was heated, the thermal radiation from the emissive source increased with increasing temperature. The flexible optical cable was constructed with 200 micron core fiber and ruggedized for turbine engine applications. The electro-optic signal processor used the ratio of intensity in two wavelength intervals to determine a digital value of the temperature. The probe tip was operated above 1900 C in a low velocity propane flame and above 1500 C at Mach .37. Probe housings, optical cables, and signal processors were constructed and environmentally tested for the temperature and vibration experienced by turbine engine sensors. This technology was used to build an optical exhaust gas sensor for a General Electric Aircraft Engines F404 turbine. The four optical probes and optical cable were a functional replacement for four thermocouple probes. The system was ground tested for 50 hours with an excess of 1000 thermal cycles. This optical temperature sensor system measured gas temperature up to the operational limit of the turbine engine.

  19. Novel diode laser-based sensors for gas sensing applications

    NASA Technical Reports Server (NTRS)

    Tittel, F. K.; Lancaster, D. G.; Richter, D.

    2000-01-01

    The development of compact spectroscopic gas sensors and their applications to environmental sensing will be described. These sensors employ mid-infrared difference-frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystals pumped by two single-frequency solid state lasers such as diode lasers, diode-pumped solid state, and fiber lasers. Ultrasensitive, highly selective, and real-time measurements of several important atmospheric trace gases, including carbon monoxide, nitrous oxide, carbon dioxide, formaldehyde [correction of formaldehye], and methane, have been demonstrated.

  20. Fiber-optic exhaust-gas sensor based on the fluorescence characteristics of Cu containing zeolites

    NASA Astrophysics Data System (ADS)

    Remillard, Jeffrey

    2000-03-01

    A single catalyst in the exhaust system can reduce the concentration of toxic gases emitted by automobiles if the engine is operated close to the stoichiometric air-fuel ratio. This is accomplished through the use of an electrochemical oxygen sensor in the exhaust stream. Near the stoichiometric point, this sensor produces a step-function response when the exhaust gas transitions from an oxygen-poor to an oxygen-rich condition. This talk describes a different kind of sensor based on the use of copper-containing zeolites that produces a proportional output. Zeolites are a class of aluminosilicate materials that have an open 3D structure containing channels and cavities. The Al sites are negatively charged and are generally compensated by cations present during formation of the zeolite. Our experiments use a zeolite designated Cu-ZSM-5, which has the protons originally present in the ZSM-5 material replaced with cupric (Cu^+2) ions. Exposure of this zeolite to a reducing gas results in the conversion of some cupric ions to cuprous (Cu^+1) ions. Subsequent exposure of the zeolite to an oxidizing gas reverses this reaction. The use of this material as a gas sensor is based on the observation that cuprous ions produce a green fluorescent emission when exposed to blue light, whereas no fluorescence is observed from cupric ions. Monitoring the fluorescence of Cu-ZSM-5 placed in a gas stream can thus provide information on the gas's reductant-to-oxidant ratio. We present the results of high temperature in-situ fluorescence spectra, intensity, and reponse-time measurements performed on samples of Cu-ZSM-5 exposed to various O_2-reductant combinations and also discuss data obtained from a single-fiber prototype sensor fabricated using a sol-gel processing technique.(J.T. Remillard et al.), Appl. Opt. 38 5306 (1999).

  1. Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Lukco, Dorothy

    2006-01-01

    Miniaturized hydrogen- and hydrocarbon-gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0 less than or equal to x less than or equal to 1) between the catalytic metal and the SiC. In prior such sensors in which the catalytic metal was the alloy PdCr, diffusion and the consequent formation of oxides and silicides of Pd and Cr during operation at high temperature were observed to cause loss of sensitivity. However, it was also observed that any PdOx layers that formed and remained at PdCr/SiC interfaces acted as barriers to diffusion, preventing further deterioration by preventing the subsequent formation of metal silicides. In the present improvement, the lesson learned from these observations is applied by placing PdOx at the catalytic metal/SiC interfaces in a controlled and uniform manner to form stable diffusion barriers that prevent formation of metal silicides. A major advantage of PdOx over other candidate diffusion-barrier materials is that PdOx is a highly stable oxide that can be incorporated into gas sensor structures by use of deposition techniques that are standard in the semiconductor industry. The PdOx layer can be used in a gas sensor structure for improved sensor stability, while maintaining sensitivity. For example, in proof-of-concept experiments, Pt/PdOx/SiC Schottky-diode gas sensors were fabricated and tested. The fabrication process included controlled sputter deposition of PdOx to a thickness of 50 Angstroms on a 400-m-thick SiC substrate, followed by deposition of Pt to a thickness of 450 Angstroms on the PdOx. The SiC substrate (400 microns in thickness) was patterned with photoresist and a Schottky-diode photomask. A lift-off process completed the definition of the Schottky-diode pattern. The sensors were tested by measuring changes in forward currents at a bias potential of 1 V during exposure to H2 in N2 at temperatures

  2. Solid-state gas sensors for breath analysis: a review.

    PubMed

    Di Natale, Corrado; Paolesse, Roberto; Martinelli, Eugenio; Capuano, Rosamaria

    2014-05-08

    The analysis of volatile compounds is an efficient method to appraise information about the chemical composition of liquids and solids. This principle is applied to several practical applications, such as food analysis where many important features (e.g. freshness) can be directly inferred from the analysis of volatile compounds. The same approach can also be applied to a human body where the volatile compounds, collected from the skin, the breath or in the headspace of fluids, might contain information that could be used to diagnose several kinds of diseases. In particular, breath is widely studied and many diseases can be potentially detected from breath analysis. The most fascinating property of breath analysis is the non-invasiveness of the sample collection. Solid-state sensors are considered the natural complement to breath analysis, matching the non-invasiveness with typical sensor features such as low-cost, easiness of use, portability, and the integration with the information networks. Sensors based breath analysis is then expected to dramatically extend the diagnostic capabilities enabling the screening of large populations for the early diagnosis of pathologies. In the last years there has been an increased attention to the development of sensors specifically aimed to this purpose. These investigations involve both specific sensors designed to detect individual compounds and non-specific sensors, operated in array configurations, aimed at clustering subjects according to their health conditions. In this paper, the recent significant applications of these sensors to breath analysis are reviewed and discussed.

  3. Grapefruit photonic crystal fiber sensor for gas sensing application

    NASA Astrophysics Data System (ADS)

    Tao, Chuanyi; Wei, Heming; Zhu, Yinian; Krishnaswamy, Sridhar

    2016-05-01

    Use of long period gratings (LPGs) formed in grapefruit photonic crystal fiber (PCF) with thin-film overlay coated on the inner surface of air holes for gas sensing is demonstrated. The finite-element method was used to numerically simulate the grapefruit PCF-LPG modal coupling characteristics and resonance spectral response with respect to the refractive index of thin-film inside the holey region. A gas analyte-induced index variation of the thin-film immobilized on the inner surface of the holey region of the fiber can be observed by a shift of the resonance wavelength. As an example, we demonstrate a 2,4-dinitrotoluene (DNT) sensor using grapefruit PCF-LPGs. The sensor exhibits a wavelength blue-shift of ˜820 pm as a result of exposure to DNT vapor with a vapor pressure of 411 ppbv at 25°C, and a sensitivity of 2 pm ppbv-1 can be achieved.

  4. Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

    PubMed Central

    Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

    2015-01-01

    We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

  5. Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection

    PubMed Central

    Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

    2008-01-01

    Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a low-cost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr2O3. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts. PMID:27873966

  6. Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection.

    PubMed

    Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

    2008-12-05

    Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a lowcost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr₂O₃. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts.

  7. Novel Self-Heated Gas Sensors Using on-Chip Networked Nanowires with Ultralow Power Consumption.

    PubMed

    Tan, Ha Minh; Manh Hung, Chu; Ngoc, Trinh Minh; Nguyen, Hugo; Duc Hoa, Nguyen; Van Duy, Nguyen; Hieu, Nguyen Van

    2017-02-22

    The length of single crystalline nanowires (NWs) offers a perfect pathway for electron transfer, while the small diameter of the NWs hampers thermal losses to tje environment, substrate, and metal electrodes. Therefore, Joule self-heating effect is nearly ideal for operating NW gas sensors at ultralow power consumption, without additional heaters. The realization of the self-heated NW sensors using the "pick and place" approach is complex, hardly reproducible, low yield, and not applicable for mass production. Here, we present the sensing capability of the self-heated networked SnO2 NWs effectively prepared by on-chip growth. Our developed self-heated sensors exhibit a good response of 25.6 to 2.5 ppm NO2 gas, while the response to 500 ppm H2, 100 ppm NH3, 100 ppm H2S, and 500 ppm C2H5OH is very low, indicating the good selectivity of the sensors to NO2 gas. Furthermore, the detection limit is very low, down to 82 parts-per-trillion. As-obtained sensing performance under self-heating mode is nearly identical to that under external heating mode. While the power consumption under self-heating mode is extremely low, around hundreds of microwatts, as scaled-down the size of the electrode is below 10 μm. The selectivity of the sensors can be controlled simply by tuning the loading power that enables simple detection of NO2 in mixed gases. Remarkable performance together with a significantly facile fabrication process of the present sensors enhances the potential application of NW sensors in next generation technologies such as electronic noses, the Internet of Things, and smartphone sensing.

  8. Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications

    NASA Astrophysics Data System (ADS)

    Penza, M.; Rossi, R.; Alvisi, M.; Serra, E.

    2010-03-01

    providing minimal sub-ppm level detection, e.g., download up to 100 ppb NO2, at the sensor temperature of 150 °C. The gas sensitivity of the CNT sensor array depends on operating temperature, showing a lower optimal temperature of maximum sensitivity for the metal-decorated CNT sensors compared to unmodified CNT sensors. Results indicate that the recovery mechanisms in the CNT chemiresistors can be altered by a rapid heating pulse from room temperature to about 110 °C. A comparison of the NO2 gas sensitivity for the chemiresistors based on disorderly networked CNTs and vertically aligned CNTs is also reported. Cross-sensitivity towards relative humidity of the CNT sensors array is investigated. Finally, the sensing properties of the metal-decorated and vertically aligned CNT sensor arrays are promising to monitor gas events in the LFG for practical applications with low power consumption and moderate sensor temperature.

  9. Systems and methods for analyzing building operations sensor data

    DOEpatents

    Mezic, Igor; Eisenhower, Bryan A.

    2015-05-26

    Systems and methods are disclosed for analyzing building sensor information and decomposing the information therein to a more manageable and more useful form. Certain embodiments integrate energy-based and spectral-based analysis methods with parameter sampling and uncertainty/sensitivity analysis to achieve a more comprehensive perspective of building behavior. The results of this analysis may be presented to a user via a plurality of visualizations and/or used to automatically adjust certain building operations. In certain embodiments, advanced spectral techniques, including Koopman-based operations, are employed to discern features from the collected building sensor data.

  10. Operating systems and network protocols for wireless sensor networks.

    PubMed

    Dutta, Prabal; Dunkels, Adam

    2012-01-13

    Sensor network protocols exist to satisfy the communication needs of diverse applications, including data collection, event detection, target tracking and control. Network protocols to enable these services are constrained by the extreme resource scarcity of sensor nodes-including energy, computing, communications and storage-which must be carefully managed and multiplexed by the operating system. These challenges have led to new protocols and operating systems that are efficient in their energy consumption, careful in their computational needs and miserly in their memory footprints, all while discovering neighbours, forming networks, delivering data and correcting failures.

  11. Fiber optic sensors for gas turbine control

    NASA Technical Reports Server (NTRS)

    Shu, Emily Yixie (Inventor); Brown, Dale Marius (Inventor); Petrucco, Louis Jacob (Inventor); Lovett, Jeffery Allan (Inventor); Daum, Wolfgang (Inventor); Dunki-Jacobs, Robert John (Inventor)

    2003-01-01

    An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

  12. Fiber optic sensors for gas turbine control

    NASA Technical Reports Server (NTRS)

    Shu, Emily Yixie (Inventor); Petrucco, Louis Jacob (Inventor); Daum, Wolfgang (Inventor)

    2005-01-01

    An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

  13. Fiber optic sensors for gas turbine control

    NASA Technical Reports Server (NTRS)

    Shu, Emily Yixie (Inventor); Brown, Dale Marius (Inventor); Petrucco, Louis Jacob (Inventor); Lovett, Jeffery Allan (Inventor); Daum, Wolfgang (Inventor); Dunki-Jacobs, Robert John (Inventor)

    1999-01-01

    An apparatus for detecting flashback occurrences in a premixed combustor system having at least one fuel nozzle includes at least one photodetector and at least one fiber optic element coupled between the at least one photodetector and a test region of the combustor system wherein a respective flame of the fuel nozzle is not present under normal operating conditions. A signal processor monitors a signal of the photodetector. The fiber optic element can include at least one optical fiber positioned within a protective tube. The fiber optic element can include two fiber optic elements coupled to the test region. The optical fiber and the protective tube can have lengths sufficient to situate the photodetector outside of an engine compartment. A plurality of fuel nozzles and a plurality of fiber optic elements can be used with the fiber optic elements being coupled to respective fuel nozzles and either to the photodetector or, wherein a plurality of photodetectors are used, to respective ones of the plurality of photodetectors. The signal processor can include a digital signal processor.

  14. Gas Sensors Based on Ceramic p-n Heterocontacts

    SciTech Connect

    Aygun, Seymen Murat

    2005-01-01

    with very high forward currents. Ga doped heterocontacts showed the highest sensitivity observed during current-time measurements as well, even though the sensor response was rather slow. Finally, a possible synergistic effect of doping both p and n-sides was studied by utilizing current-time measurements for 1.5 mol% Ni-CuO/1.5 mol% Ga-ZnO heterocontact. A sensitivity value of ~5.1 was obtained with the fastest response among all the samples. The time needed to reach 90% coverage was lowered by a factor of 4 when compared to the pure heterocontact and the time needed to reach 70% coverage was just over one minute. Heterocontact gas sensors are promising candidates for high temperature sensor applications. Today, Si-based microelectromechanical system (MEMS) technology has shown great promise for developing novel devices such as pressure sensors, chemical sensors, and temperature sensors through complex designs. However, the harsh thermal, vibrational, and corrosive environments common to many aerospace applications impose severe limitations on their use. Sensors based on ceramic p-n heterocontacts are promising alternatives because of their inherent corrosion resistance and environmental stability. The other advantages include their inherent tuning ability to differentiate between different reducing gases and a possible cost efficient production of a wireless sensor. Being a capacitive type sensor, its output can be transformed into a passive wireless device by creating a tuned LC circuit. In this way, the sensor output (the capacitance) can be accessed remotely by measuring the resonant frequency. The relatively simple structure of heterocontacts makes it suitable for thick film fabrication techniques to make sensor packages.

  15. Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors

    PubMed Central

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

  16. Nanocrystalline SnO2:F thin films for liquid petroleum gas sensors.

    PubMed

    Chaisitsak, Sutichai

    2011-01-01

    This paper reports the improvement in the sensing performance of nanocrystalline SnO(2)-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO(2) films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO(2) with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO(2):F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO(2) was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO(2):F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection.

  17. Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

    PubMed Central

    Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

    2010-01-01

    Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

  18. Optical Breath Gas Sensor for Extravehicular Activity Application

    NASA Technical Reports Server (NTRS)

    Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S.; Chullen, Cinda; Falconi, Eric A.; McMillin, Summer

    2013-01-01

    The function of the infrared gas transducer used during extravehicular activity in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation portable life support system (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Space Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode spectrometer based on wavelength modulation spectroscopy is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode-based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen channel using a vertical cavity surface emitting laser. Both prototypes are controlled digitally with a field-programmable gate array/microcontroller architecture. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU.

  19. Microdischarge-based pressure sensors utilizing multiple cathodes for operation up to 1000^oC

    NASA Astrophysics Data System (ADS)

    Wright, Scott; Gianchandani, Yogesh

    2009-10-01

    High temperature pressure sensors have uses in numerous industrial sectors including gas turbine engines, coal boilers, internal combustion engines, and oil/gas exploration machinery. Microdischarges are well-suited for high-temperature operation because of the inherently high temperatures of the ionized species that sustain them. This work describes sensors that operate by measuring the change, with pressure, in the spatial current distribution of pulsed DC microdischarges. The spatial current distribution is determined from the current in two cathodes, with different interelectrode spacing, and the differential current is treated as the output. At low pressures, current favors the farthest cathode while at high pressures, the opposite occurs. Two versions of the sensors are reported. The first type uses 3-D arrays of horizontal bulk metal electrodes embedded in quartz substrates with electrode diameters of 1--2 mm and 50--100-μm interelectrode spacing. These devices were operated in nitrogen over a range of 10--2000 Torr, at temperatures as high as 1000^oC. The maximum measured sensitivity was 5420 ppm/Torr, while the temperature coefficient of sensitivity was as low as -550 ppm/K. Sensors of the second type use planar electrodes and have active areas as small as 0.13 mm^2 with a maximum sensitivity of 9800 ppm/Torr.

  20. Data set from gas sensor array under flow modulation☆

    PubMed Central

    Ziyatdinov, Andrey; Fonollosa, Jordi; Fernández, Luis; Gutiérrez-Gálvez, Agustín; Marco, Santiago; Perera, Alexandre

    2015-01-01

    Recent studies in neuroscience suggest that sniffing, namely sampling odors actively, plays an important role in olfactory system, especially in certain scenarios such as novel odorant detection. While the computational advantages of high frequency sampling have not been yet elucidated, here, in order to motivate further investigation in active sampling strategies, we share the data from an artificial olfactory system made of 16 MOX gas sensors under gas flow modulation. The data were acquired on a custom set up featured by an external mechanical ventilator that emulates the biological respiration cycle. 58 samples were recorded in response to a relatively broad set of 12 gas classes, defined from different binary mixtures of acetone and ethanol in air. The acquired time series show two dominant frequency bands: the low-frequency signal corresponds to a conventional response curve of a sensor in response to a gas pulse, and the high-frequency signal has a clear principal harmonic at the respiration frequency. The data are related to the study in [1], and the data analysis results reported there should be considered as a reference point. The data presented here have been deposited to the web site of The University of California at Irvine (UCI) Machine Learning Repository (https://archive.ics.uci.edu/ml/datasets/Gas+sensor+array+under+flow+modulation). The code repository for reproducible analysis applied to the data is hosted at the GutHub web site (https://github.com/variani/pulmon). The data and code can be used upon citation of [1]. PMID:26217733

  1. Future electro-optical sensors and processing in urban operations

    NASA Astrophysics Data System (ADS)

    Grönwall, Christina; Schwering, Piet B.; Rantakokko, Jouni; Benoist, Koen W.; Kemp, Rob A. W.; Steinvall, Ove; Letalick, Dietmar; Björkert, Stefan

    2013-10-01

    In the electro-optical sensors and processing in urban operations (ESUO) study we pave the way for the European Defence Agency (EDA) group of Electro-Optics experts (IAP03) for a common understanding of the optimal distribution of processing functions between the different platforms. Combinations of local, distributed and centralized processing are proposed. In this way one can match processing functionality to the required power, and available communication systems data rates, to obtain the desired reaction times. In the study, three priority scenarios were defined. For these scenarios, present-day and future sensors and signal processing technologies were studied. The priority scenarios were camp protection, patrol and house search. A method for analyzing information quality in single and multi-sensor systems has been applied. A method for estimating reaction times for transmission of data through the chain of command has been proposed and used. These methods are documented and can be used to modify scenarios, or be applied to other scenarios. Present day data processing is organized mainly locally. Very limited exchange of information with other platforms is present; this is performed mainly at a high information level. Main issues that arose from the analysis of present-day systems and methodology are the slow reaction time due to the limited field of view of present-day sensors and the lack of robust automated processing. Efficient handover schemes between wide and narrow field of view sensors may however reduce the delay times. The main effort in the study was in forecasting the signal processing of EO-sensors in the next ten to twenty years. Distributed processing is proposed between hand-held and vehicle based sensors. This can be accompanied by cloud processing on board several vehicles. Additionally, to perform sensor fusion on sensor data originating from different platforms, and making full use of UAV imagery, a combination of distributed and

  2. Design of Selective Gas Sensors Using Additive-Loaded In2O3 Hollow Spheres Prepared by Combinatorial Hydrothermal Reactions

    PubMed Central

    Kim, Sun-Jung; Hwang, In-Sung; Kang, Yun Chan; Lee, Jong-Heun

    2011-01-01

    A combinatorial hydrothermal reaction has been used to prepare pure and additive (Sb, Cu, Nb, Pd, and Ni)-loaded In2O3 hollow spheres for gas sensor applications. The operation of Pd- and Cu-loaded In2O3 sensors at 371 °C leads to selective H2S detection. Selective detection of CO and NH3 was achieved by the Ni-In2O3 sensor at sensing temperatures of 371 and 440 °C, respectively. The gas responses of six different sensors to NH3, H2S, H2, CO and CH4 produced unique gas sensing patterns that can be used for the artificial recognition of these gases. PMID:22346661

  3. Hydrogen Sensors Boost Hybrids; Today's Models Losing Gas?

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Advanced chemical sensors are used in aeronautic and space applications to provide safety monitoring, emission monitoring, and fire detection. In order to fully do their jobs, these sensors must be able to operate in a range of environments. NASA has developed sensor technologies addressing these needs with the intent of improving safety, optimizing combustion efficiencies, and controlling emissions. On the ground, the chemical sensors were developed by NASA engineers to detect potential hydrogen leaks during Space Shuttle launch operations. The Space Shuttle uses a combination of hydrogen and oxygen as fuel for its main engines. Liquid hydrogen is pumped to the external tank from a storage tank located several hundred feet away. Any hydrogen leak could potentially result in a hydrogen fire, which is invisible to the naked eye. It is important to detect the presence of a hydrogen fire in order to prevent a major accident. In the air, the same hydrogen-leak dangers are present. Stress and temperature changes can cause tiny cracks or holes to form in the tubes that line the Space Shuttle s main engine nozzle. Such defects could allow the hydrogen that is pumped through the nozzle during firing to escape. Responding to the challenges associated with pinpointing hydrogen leaks, NASA endeavored to improve propellant leak-detection capabilities during assembly, pre-launch operations, and flight. The objective was to reduce the operational cost of assembling and maintaining hydrogen delivery systems with automated detection systems. In particular, efforts have been focused on developing an automated hydrogen leak-detection system using multiple, networked hydrogen sensors that are operable in harsh conditions.

  4. Multiplexed Sensor for Synthesis Gas Compsition and Temperature

    SciTech Connect

    Steven Buckley; Reza Gharavi; Marco Leon

    2007-10-01

    The overall goal of this project has been to develop a highly sensitive, multiplexed TDL-based sensor for CO{sub 2}, CO, H{sub 2}O (and temperature), CH{sub 4}, H{sub 2}S, and NH{sub 3}. Such a sensor was designed with so-called 'plug-and-play' characteristics to accommodate additional sensors, and provided in situ path-integrated measurements indicative of average concentrations at speeds suitable for direct gasifier control. The project developed the sensor and culminated in a real-world test of the underlying technology behind the sensor. During the project, new underlying measurements of spectroscopic constants for all of the gases of interest performed, in custom cells built for the project. The envisioned instrument was built from scratch from component lasers, fiber optics, amplifier blocks, detectors, etc. The sensor was tested for nearly a week in an operational power plant. The products of this research are expected to have a direct impact on gasifier technology and the production of high-quality syngas, with substantial broader application to coal and other energy systems. This report is the final technical report on project DE-FG26-04NT42172. During the project we completed all of the milestones planned in the project, with a modification of milestone (7) required due to lack of funding and personnel.

  5. Extremely sensitive CWA analyzer based on a novel optical pressure sensor in photoacoustic gas analysis

    NASA Astrophysics Data System (ADS)

    Kauppinen, Jyrki K.; Koskinen, Vesa; Uotila, Juho; Kauppinen, Ismo K.

    2004-12-01

    Major improvement into the sensitivity of broadband Fourier transform infrared (FTIR) spectrometers, used in gas analysis, can be achieved by a photoacoustic detection system, which bases on a recently introduced optical pressure sensor. The sensor is a cantilever-type microphone with interferometric measurement of its free end displacement. By using a preliminary prototype of the photoacoustic gas detector, equipped with the proposed sensor and a black body radiation source, a detection limit in the sub-ppb range was obtained for e.g. methane gas. The limit, obtained in non-resonant operation mode, is very close to the best photoacoustic results achieved with powerfull laser sources and by exploiting the cell resonances. It is also orders of magnitude better than any measurement with a black body radiation source. Furthermore, the ultimate sensitivity leads on to very small detection limits also for several chemical warfare agents (CWA) e.g. sarin, tabun and mustard. The small size of the sensor and its great thermal stability enables the construction of an extremely sensitive portable CWA analyzer in the near future.

  6. Fabrication of SnO2 based CO gas sensor device using thick film technology

    NASA Astrophysics Data System (ADS)

    Hermida, I. D. P.; Wiranto, G.; Hiskia; Nopriyanti, R.

    2016-11-01

    This research was aimed at fabricating a CO gas sensor based on SnO2 material synthesized using sol-gel method. The sensor components include thin film gold electrode and a PdAg heater screen printed on the backside of the alumina substrate. The device was tested to study the effect of temperature variation on the resistivity of the heater component, and the response of the SnO2 sensitive layer to 10 ppm CO gas. The SnO2 layer was characterized using SEM and EDS to determine the morphology and composition of the material. It was found that the SnO2 sensitive layer contained 21.21% C atoms, 22.43% O atoms, 14.98% Si atoms, 0.34% Cr atoms, 1.16% Ag atoms, 1.78% Sn atoms, and 38.11% Au atoms. The sensor sensitivity to CO gas increased with increasing temperature. The Operational temperature of this sensor was 95° C with the highest sensitivity value obtained was 16.59.

  7. Study on the micro-heater geometry in In,2O3 micro electro mechanical systems gas sensor platforms and effects on NO2 gas detecting performances.

    PubMed

    Choi, Woo-Seok; Kim, Bum-Joon; Lee, Hoi-Jung; Choi, Jung-Woon; Kim, Si-Dong; Min, Nam-Ki

    2012-02-01

    Micro electro mechanical systems (MEMS) platforms for gas sensing devices with the co-planar type micro-heaters were designed, fabricated and its effects on the In2O3 gas sensors were investigated. Micro-heaters in MEMS gas sensor platforms were designed in the four-type heater patterns with different geometries. Electro-thermal characterizations showed that the designed platforms had highly thermal efficiency because the micro hot-plate structures were formed in the diaphragm and the thermal efficiencies were analyzed for all of 16 models and compared with each other, respectively. The designed micro-platforms were fabricated by MEMS process, and Indium oxide (In2O3) nanoparticles were synthesized by sol-gel process and dropped on the MEMS platforms for detecting the noxious oxide gas (NO2) Fabricated micro-platforms had a very low power consumption in the fabricated 16-type models, especially, the minimum power consumption was 41 mW at the operating temperature of 250 degrees C. After experiments on gas sensing characteristics to NO2 gases, fabricated In2O3 gas sensors had almost the same gas sensitivity (Rs) at the operation temperature of 250 degrees C. It is concluded that the micro-heater geometries, pattern shapes and sizes, can be influential on the power consumption of the devices and its gas sensing characteristics.

  8. Space Shuttle Proximity Operation Sensor Study

    NASA Technical Reports Server (NTRS)

    Weber, C. L.; Alem, W. K.

    1978-01-01

    The performance of the Kuband radar was analyzed in detail, and the performance was updated and summarized. In so doing, two different radar design philosophies were described, and the corresponding differences in losses were enumerated. The resulting design margins were determined for both design philosophies and for both the designated and nondesignated range modes of operation. In some cases, the design margin was about zero, and in other cases it was significantly less than zero. With the point of view described above, the recommended solution is to allow more scan time but at the present scan rate. With no other changes in the present configuration, the radar met design detection specifications for all design philosophies at a range of 11.3 nautical miles.

  9. Operations and Maintenance Manual, Atmospheric Contaminant Sensor, Revision B.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    The sensor is a mass spectrometer system which continuously monitors the atmospheric constituents of hydrogen, water vapor, nitrogen, oxygen, and carbon dioxide, and monitors the Freons on a demand sampling basis. The manual provides a system description, operational procedures, and maintenance and troubleshooting instructions. Circuit diagrams…

  10. Operations and maintenance manual, atmospheric contaminant sensor, revision B

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The sensor is a mass spectrometer system which continuously monitors the atmospheric constituents of hydrogen, water vapor, nitrogen, oxygen, and carbon dioxide, and monitors the Freons on a demand sampling basis. The manual provides a system description, operational procedures, and maintenance and troubleshooting instructions. Circuit diagrams are included.

  11. Surfactant assisted solid-state synthesis and gas sensor application of a SWCNT/SnO2 nanocomposite material.

    PubMed

    Lu, Jun; Ma, Anson; Yang, Shihe; Ng, Ka Ming

    2007-01-01

    Although tin oxide has been the most widely investigated metal oxide material for gas detection, it suffers from the large resistance and high operating temperature. This could be overcome by hybridization with nanostructured carbon. In this work, tin oxide nanoparticles with ultrasmall sizes of 1-3 nm have been uniformly coated onto bundles of single-walled carbon nanotubes by a surfactant assisted solid state synthesis approach for the first time. Gas sensor properties of the as-synthesized nanocomposite material toward NO2 (from 5 to 60 ppm) are measured at 150 degrees C. Compared to the pure carbon tubes gas sensors, the nanocomposite gas sensor responds to NO2 in low concentrations with good linearity, high sensitivity, and fast recovery, while working at a relatively low temperature.

  12. Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

    NASA Astrophysics Data System (ADS)

    Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

    2016-10-01

    In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

  13. Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems

    SciTech Connect

    Pickrell, Gary; Scott, Brian

    2014-06-30

    This report covers the technical progress on the program “Novel Modified Optical Fibers for High Temperature In-Situ Miniaturized Gas Sensors in Advanced Fossil Energy Systems”, funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Materials Science & Engineering and Electrical & Computer Engineering Departments at Virginia Tech, and summarizes technical progress from July 1st, 2005 –June 30th, 2014. The objective of this program was to develop novel fiber materials for high temperature gas sensors based on evanescent wave absorption in optical fibers. This project focused on two primary areas: the study of a sapphire photonic crystal fiber (SPCF) for operation at high temperature and long wavelengths, and a porous glass based fiber optic sensor for gas detection. The sapphire component of the project focused on the development of a sapphire photonic crystal fiber, modeling of the new structures, fabrication of the optimal structure, development of a long wavelength interrogation system, testing of the optical properties, and gas and temperature testing of the final sensor. The fabrication of the 6 rod SPCF gap bundle (diameter of 70μm) with a hollow core was successfully constructed with lead-in and lead-out 50μm diameter fiber along with transmission and gas detection testing. Testing of the sapphire photonic crystal fiber sensor capabilities with the developed long wavelength optical system showed the ability to detect CO2 at or below 1000ppm at temperatures up to 1000°C. Work on the porous glass sensor focused on the development of a porous clad solid core optical fiber, a hollow core waveguide, gas detection capabilities at room and high temperature, simultaneous gas species detection, suitable joining technologies for the lead-in and lead-out fibers and the porous sensor, sensor system sensitivity improvement, signal processing improvement, relationship between pore structure and fiber

  14. Sensors for measuring primary zone equivalence ratio in gas turbine combustors

    NASA Astrophysics Data System (ADS)

    Bandaru, Ramarao V.; Miller, Sean; Lee, Jong-Guen; Santavicca, Domenic A.

    1999-01-01

    In lean-premixed combustion, the narrow range of operating conditions where stable, low-emissions combustion, is achieved make it necessary for a fuel-air equivalence ratio sensor to be incorporated into the combustor. Such a sensor should be capable of determining nozzle-to-nozzle variations in the equivalence ratio, and have a reasonably fast response time so that the control mechanism can meter the flowrates accordingly. This paper describes the development of a flame chemiluminescence based equivalence ratio sensor, which can be installed in the individual nozzles of a gas turbine combustor. The first stage of the development involves studying the chemiluminescence characteristics of CH* and CO2* in a dump combustor. It was observed that fuel-air mixedness does not affect the overall flame chemiluminescence, and inlet temperature variations over 50K have not produced discernible differences in the chemiluminescence intensities. Combustor velocities do affect the flame chemiluminescence intensities, and this parameter has to be taken into account while developing the sensor. An optical fiber based sensor, which can easily installed in a combustor, has been designed. Based on this study, a methodology for determining the equivalence ratio from the chemiluminescent intensities and flowrates is proposed for use with the sensor under development.

  15. Data set from chemical sensor array exposed to turbulent gas mixtures

    PubMed Central

    Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Huerta, Ramón

    2015-01-01

    A chemical detection platform composed of 8 chemo-resistive gas sensors was exposed to turbulent gas mixtures generated naturally in a wind tunnel. The acquired time series of the sensors are provided. The experimental setup was designed to test gas sensors in realistic environments. Traditionally, chemical detection systems based on chemo-resistive sensors include a gas chamber to control the sample air flow and minimize turbulence. Instead, we utilized a wind tunnel with two independent gas sources that generate two gas plumes. The plumes get naturally mixed along a turbulent flow and reproduce the gas concentration fluctuations observed in natural environments. Hence, the gas sensors can capture the spatio-temporal information contained in the gas plumes. The sensor array was exposed to binary mixtures of ethylene with either methane or carbon monoxide. Volatiles were released at four different rates to induce different concentration levels in the vicinity of the sensor array. Each configuration was repeated 6 times, for a total of 180 measurements. The data is related to “Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry”, by Fonollosa et al. [1]. The dataset can be accessed publicly at the UCI repository upon citation of [1]: http://archive.ics.uci.edu/ml/datasets/Gas+senso+rarray+exposed+to+turbulent+gas+mixtures. PMID:26217747

  16. Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection

    NASA Technical Reports Server (NTRS)

    Li, Jing; Lu, Yijiang

    2005-01-01

    A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

  17. Fabrication and characterization of nano-gas sensor arrays

    SciTech Connect

    Hassan, H. S. Kashyout, A. B.; Morsi, I. Nasser, A. A. A. Raafat, A.

    2015-03-30

    A novel structures of Nanomaterials gas sensors array constructed using ZnO, and ZnO doped with Al via sol-gel technique. Two structure arrays are developed; the first one is a double sensor array based on doping with percentages of 1% and 5%. The second is a quadrature sensor array based on several doping ratios concentrations (0%, 1%, 5% and 10%). The morphological structures of prepared ZnO were revealed using scanning electron microscope (SEM). X-ray diffraction (XRD) patterns reveal a highly crystallized wurtzite structure and used for identifying phase structure and chemical state of both ZnO and ZnO doped with Al under different preparation conditions and different doping ratios. Chemical composition of Al-doped ZnO nanopowders was performed using energy dispersive x-ray (EDS) analysis. The electrical characteristics of the sensor are determined by measuring the two terminal sensor’s output resistance for O{sub 2}, H{sub 2} and CO{sub 2} gases as a function of temperature.

  18. Continued Optical Sensor Operations in a Laser Environment

    DTIC Science & Technology

    2011-02-16

    NOTE AIR WAR COLLEGE AIR UNIVERSITY CONTINUED OPTICAL SENSOR OPERATIONS IN A LASER ENVIRONMENT by William J. Diehl, CDR, USN A Research...1 Optical Region of the Electromagnetic Spectrum….………..……………………….….…2 Introduction to Lasers ...Optical Sensor Vulnerabilities to Lasers …………………………………….12 Recommendations………………………….……………………………………….……20 Conclusion

  19. Power consumption analysis of operating systems for wireless sensor networks.

    PubMed

    Lajara, Rafael; Pelegrí-Sebastiá, José; Perez Solano, Juan J

    2010-01-01

    In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems--TinyOS v1.0, TinyOS v2.0, Mantis and Contiki--running on Tmote Sky and MICAz devices. With the objective of ensuring a fair evaluation, a benchmark composed of four applications has been developed, covering the most typical tasks that a Wireless Sensor Network performs. The results show the instant and average current consumption of the devices during the execution of these applications. The experimental measurements provide a good insight into the power mode in which the device components are running at every moment, and they can be used to compare the performance of different operating systems executing the same tasks.

  20. Power Consumption Analysis of Operating Systems for Wireless Sensor Networks

    PubMed Central

    Lajara, Rafael; Pelegrí-Sebastiá, José; Perez Solano, Juan J.

    2010-01-01

    In this paper four wireless sensor network operating systems are compared in terms of power consumption. The analysis takes into account the most common operating systems—TinyOS v1.0, TinyOS v2.0, Mantis and Contiki—running on Tmote Sky and MICAz devices. With the objective of ensuring a fair evaluation, a benchmark composed of four applications has been developed, covering the most typical tasks that a Wireless Sensor Network performs. The results show the instant and average current consumption of the devices during the execution of these applications. The experimental measurements provide a good insight into the power mode in which the device components are running at every moment, and they can be used to compare the performance of different operating systems executing the same tasks. PMID:22219688

  1. Measurement system for nitrous oxide based on amperometric gas sensor

    NASA Astrophysics Data System (ADS)

    Siswoyo, S.; Persaud, K. C.; Phillips, V. R.; Sneath, R.

    2017-03-01

    It has been well known that nitrous oxide is an important greenhouse gas, so monitoring and control of its concentration and emission is very important. In this work a nitrous oxide measurement system has been developed consisting of an amperometric sensor and an appropriate lab-made potentiostat that capable measuring picoampere current ranges. The sensor was constructed using a gold microelectrode as working electrode surrounded by a silver wire as quasi reference electrode, with tetraethyl ammonium perchlorate and dimethylsulphoxide as supporting electrolyte and solvent respectively. The lab-made potentiostat was built incorporating a transimpedance amplifier capable of picoampere measurements. This also incorporated a microcontroller based data acquisition system, controlled by a host personal computer using a dedicated computer program. The system was capable of detecting N2O concentrations down to 0.07 % v/v.

  2. Potassium polytitanate gas-sensor study by impedance spectroscopy.

    PubMed

    Fedorov, F S; Varezhnikov, A S; Kiselev, I; Kolesnichenko, V V; Burmistrov, I N; Sommer, M; Fuchs, D; Kübel, C; Gorokhovsky, A V; Sysoev, V V

    2015-10-15

    Nanocrystalline potassium polytitanates K2O·nTiO2·mH2O represent a new type of semiconducting compounds which are characterized by a high specific surface that makes them promising for use in gas sensors. In this work, we have studied potassium polytitanate mesoporous nanoparticle agglomerates placed over a SiO2/Si substrate equipped with multiple coplanar electrodes to measure the electrical response to various organic vapors, 1000 ppm of concentration, mixed with air by impedance spectrometry in range of the 10(-2)-10(6) Hz. The recorded impedance data for each sensor segment are associated with RC components of an equivalent circuit which are applied to selectively recognize the test vapors exploiting a "multisensor array" approach.

  3. Batch-processed semiconductor gas sensor array for the selective detection of NOx in automotive exhaust gas

    NASA Astrophysics Data System (ADS)

    Jang, Hani; Kim, Minki; Kim, Yongjun

    2016-12-01

    This paper reports on a semiconductor gas sensor array to detect nitrogen oxides (NOx) in automotive exhaust gas. The proposed semiconductor gas sensor array consisted of one common electrode and three individual electrodes to minimize the size of the sensor array, and three sensing layers [TiO2 + SnO2 (15 wt%), SnO2, and Ga2O3] were deposited using screen printing. In addition, sensing materials were sintered under the same conditions in order to take advantage of batch processing. The sensing properties of the proposed sensor array were verified by experimental measurements, and the selectivity improved by using pattern recognition.

  4. Optical Breath Gas Sensor for Extravehicular Activity Application

    NASA Technical Reports Server (NTRS)

    Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S> ; Chullen, Cinda; Falconi, Eric A.

    2012-01-01

    The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation Portable Life Support System (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) spectrometer based on wavelength modulation spectroscopy (WMS) is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen (O2) channel using a vertical cavity surface emitting laser (VCSEL). Both prototypes are controlled digitally with a field-programmable gate array (FPGA)/microcontroller architecture. Based on the results of the initial instrument development, further prototype development and testing of instruments leveraging the lessons learned were desired. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU. .

  5. Gas sensor characterization at low concentrations of natural oils

    NASA Astrophysics Data System (ADS)

    Sambemana, H.; Siadat, M.; Lumbreras, M.

    2009-05-01

    Inhalation of essential oils can be used in aromatherapy due to their activating or relaxing effects. The study of these effects requires behavioral measurements on living subjects, by varying the nature and also the quantity of the volatile substances to be present in the atmosphere. So, to permit the evaluation of therapeutic effects of a variety of natural oils, we propose to develop an automatic diffusion/detection system capable to create an ambient air with low stabilized concentration of chosen oil. In this work, we discuss the performance of an array of eight gas sensors to discriminate low and constant concentrations of a chosen natural oil.

  6. Selective, pulsed CVD of platinum on microfilament gas sensors

    SciTech Connect

    Manginell, R.P.; Smith, J.H.; Ricco, A.J.; Moreno, D.J.; Hughes, R.C.; Huber, R.J.; Senturia, S.D.

    1996-05-01

    A post-processing, selective micro-chemical vapor deposition (``micro-CVD``) technology for the deposition of catalytic films on surface-micromachined, nitride-passivated polysilicon filaments has been investigated. Atmospheric pressure deposition of Pt on microfilaments was accomplished by thermal decomposition of Pt acetylacetonate; deposition occurs selectively only on those filaments which are electrically heated. Catalyst morphology, characterized by SEM, can be controlled by altering deposition time, filament temperature, and through the use of pulsed heating of the filament during deposition. Morphology plays an important role in determining the sensitivity of these devices when used as combustible gas sensors.

  7. Multi-walled carbon nanotubes plastic NH3 gas sensor

    NASA Astrophysics Data System (ADS)

    Isa, Siti S. Mat; Ramli, Muhammad M.; Jamlos, M. F.; Hambali, N. A. M. Ahmad; Isa, M. Mohamad; Kasjoo, S. R.; Ahmad, N.; Nor, N. I. M.; Khalid, N.

    2017-03-01

    Multi-walled Carbon Nanotubes (MWCNTs) functionalized -COOH was used as the sensing material. The MWCNTs suspension was then deposited on the plastic substrate using vacuum filtration method, hence created uniform thin film carbon nanotubes network. Plastic membrane was chosen as the substrate in order to produce flexible, lightweight, wearable and low cost sensor. This device was exposed to ammonia gas (NH3) at two different concentrations; 19.2 and 231.4 ppm. The device shows high sensitivity at 23.4 % when exposed to 231.4 ppm NH3 and less sensitivity at 4.39 % for 19.2 ppm NH3 exposure.

  8. Gold nanoparticles promote amorphous carbon to be ammonia gas sensor

    NASA Astrophysics Data System (ADS)

    Hsu, Hua-Shu; Ju, Shin-Pon; Sun, Shih-Jye; Chou, Hsiung; Chia, C. H.

    2016-05-01

    As gold-nanoparticles-embedded in amorphous carbon films the sp 3 carbon orbits near the interface will be partially transferred to sp 2. The Raman spectrum measurements as well as the molecular-dynamics simulations used the second reactive empirical bond order (REBO) potential simulating the interatomic force between carbon atoms both confirm the orbital transformations. The amorphous carbon films are initially inert to gases, while the films embedded with gold nanoparticles exhibit the increase of resistance in ammonia atmosphere. Namely, gold-nanoparticles-embedded amorphous carbon films become the candidate for ammonia gas sensor materials.

  9. Emissions from oil and natural gas operations in northeastern Utah

    NASA Astrophysics Data System (ADS)

    Petron, G.; Kofler, J. D.; Frost, G. J.; Miller, B. R.; Edwards, P. M.; Dube, W. P.; Montzka, S. A.; Helmig, D.; Hueber, J.; Karion, A.; Sweeney, C.; Conley, S. A.; Brown, S. S.; Geiger, F.; Warneke, C.; Martin, R. S.; Andrews, A. E.; Dlugokencky, E. J.; Lang, P. M.; Trainer, M.; Hardesty, R.; Schnell, R. C.; Tans, P. P.

    2012-12-01

    The Uintah oil and natural gas Basin in Northeastern Utah experienced several days of high ozone levels in early 2011 during cold temperature inversions. To study the chemical and meteorological processes leading to these wintertime ozone pollution events, the State of Utah, EPA region 8 and oil and gas operators pulled together a multi-agency research team, including NOAA ESRL/CIRES scientists. The data gathering took place between January 15 and February 29, 2012.To document the chemical signature of various sources in the Basin, we outfitted a passenger van with in-situ analyzers (Picarro: CH4, CO2, CO, H2O, 13CH4; NOxCaRD: NO, NOx, 2B & NOxCaRD: O3) meteorological sensors, GPS units, discrete flask sampling apparatus, as well as a data logging and "real-time" in-situ data visualization system. The instrumented van, called Mobile Lab, also hosted a KIT Proton Transfer Reaction Mass Spectrometer (suite of VOCs in situ measurements) for part of the campaign. For close to a month, the Mobile Lab traveled the roads of the oil and gas field, documenting ambient levels of several tracers. Close to 180 valid air samples were collected in February by the Mobile Lab for future analysis in the NOAA and CU/INSTAAR labs in Boulder. At the same time as the surface effort was going on, an instrumented light aircraft conducted transects over the Basin collecting air samples mostly in the boundary layer and measuring in situ the following species CH4, CO2, NO2, O3. We will present some of the data collected by the Mobile Lab and the aircraft and discuss analysis results.

  10. Operating systems for wireless sensor networks: a survey.

    PubMed

    Farooq, Muhammad Omer; Kunz, Thomas

    2011-01-01

    This paper presents a survey on the current state-of-the-art in Wireless Sensor Network (WSN) Operating Systems (OSs). In recent years, WSNs have received tremendous attention in the research community, with applications in battlefields, industrial process monitoring, home automation, and environmental monitoring, to name but a few. A WSN is a highly dynamic network because nodes die due to severe environmental conditions and battery power depletion. Furthermore, a WSN is composed of miniaturized motes equipped with scarce resources e.g., limited memory and computational abilities. WSNs invariably operate in an unattended mode and in many scenarios it is impossible to replace sensor motes after deployment, therefore a fundamental objective is to optimize the sensor motes' life time. These characteristics of WSNs impose additional challenges on OS design for WSN, and consequently, OS design for WSN deviates from traditional OS design. The purpose of this survey is to highlight major concerns pertaining to OS design in WSNs and to point out strengths and weaknesses of contemporary OSs for WSNs, keeping in mind the requirements of emerging WSN applications. The state-of-the-art in operating systems for WSNs has been examined in terms of the OS Architecture, Programming Model, Scheduling, Memory Management and Protection, Communication Protocols, Resource Sharing, Support for Real-Time Applications, and additional features. These features are surveyed for both real-time and non-real-time WSN operating systems.

  11. Operating Systems for Wireless Sensor Networks: A Survey

    PubMed Central

    Farooq, Muhammad Omer; Kunz, Thomas

    2011-01-01

    This paper presents a survey on the current state-of-the-art in Wireless Sensor Network (WSN) Operating Systems (OSs). In recent years, WSNs have received tremendous attention in the research community, with applications in battlefields, industrial process monitoring, home automation, and environmental monitoring, to name but a few. A WSN is a highly dynamic network because nodes die due to severe environmental conditions and battery power depletion. Furthermore, a WSN is composed of miniaturized motes equipped with scarce resources e.g., limited memory and computational abilities. WSNs invariably operate in an unattended mode and in many scenarios it is impossible to replace sensor motes after deployment, therefore a fundamental objective is to optimize the sensor motes’ life time. These characteristics of WSNs impose additional challenges on OS design for WSN, and consequently, OS design for WSN deviates from traditional OS design. The purpose of this survey is to highlight major concerns pertaining to OS design in WSNs and to point out strengths and weaknesses of contemporary OSs for WSNs, keeping in mind the requirements of emerging WSN applications. The state-of-the-art in operating systems for WSNs has been examined in terms of the OS Architecture, Programming Model, Scheduling, Memory Management and Protection, Communication Protocols, Resource Sharing, Support for Real-Time Applications, and additional features. These features are surveyed for both real-time and non-real-time WSN operating systems. PMID:22163934

  12. Gas-leak localization using distributed ultrasonic sensors

    NASA Astrophysics Data System (ADS)

    Huseynov, Javid; Baliga, Shankar; Dillencourt, Michael; Bic, Lubomir; Bagherzadeh, Nader

    2009-03-01

    We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators are used for approximating the source location when closed-form solutions fail in the presence of ambient background nuisance and inherent electronic noise. The proposed localization algorithms were implemented and tested using a Java-based simulation platform connected to four or more distributed MEMS microphones observing a broadband nitrogen leak from an orifice. The performance of centralized and decentralized algorithms under ED and TDOA schemes is analyzed and compared in terms of communication overhead and accuracy in presence of additive white Gaussian noise (AWGN).

  13. Tellurium nano-structure based NO gas sensor.

    PubMed

    Kumar, Vivek; Sen, Shashwati; Sharma, M; Muthe, K P; Jagannath; Gaur, N K; Gupta, S K

    2009-09-01

    Tellurium nanotubes were grown on bare and silver/gold nanoparticle (nucleation centers) deposited silicon substrates by vacuum deposition technique at a substrate temperature of 100 degrees C under high vacuum conditions. Silver and gold nanoparticles prepared on (111) oriented silicon substrates were found to act as nucleation centers for growth of Tellurium nanostructures. Density of nanotubes was found to increase while their diameter reduced when grown using metallic nanoparticle template. These Te nanostructures were investigated for their gas sensitivity. Tellurium nanotubes on Ag templates showed better response to NO in comparison to H2S and NH3 gases. Selectivity in response to NO was improved in comparison to Te thin film sensors reported earlier. The gas sensing mechanism was investigated using Raman and X-ray photoelectron spectroscopy techniques. The interaction of NO is seen to yield increased adsorption of oxygen that in turn increases hole density and conductivity in the material.

  14. Gas sensing performance of nano zinc oxide sensors

    NASA Astrophysics Data System (ADS)

    Sharma, Shiva; Chauhan, Pratima

    2016-04-01

    We report nano Zinc Oxide (ZnO) synthesized by sol-gel method possessing the crystallite size which varies from 25.17 nm to 47.27 nm. The Scanning electron microscope (SEM) image confirms the uniform distribution of nanograins with high porosity. The Energy dispersion X-ray (EDAX) spectrum gives the atomic composition of Zn and O in ZnO powders and confirms the formation of nano ZnO particles. These factors reveals that Nano ZnO based gas sensors are highly sensitive to Ammonia gas (NH3) at room temperature, indicating the maximum response 86.8% at 800 ppm with fast response time and recovery time of 36 sec and 23 sec respectively.

  15. High-performance gas sensors with temperature measurement

    PubMed Central

    Zhang, Yong; Li, Shengtao; Zhang, Jingyuan; Pan, Zhigang; Min, Daomin; Li, Xin; Song, Xiaoping; Liu, Junhua

    2013-01-01

    There are a number of gas ionization sensors using carbon nanotubes as cathode or anode. Unfortunately, their applications are greatly limited by their multi-valued sensitivity, one output value corresponding to several measured concentration values. Here we describe a triple-electrode structure featuring two electric fields with opposite directions, which enable us to overcome the multi-valued sensitivity problem at 1 atm in a wide range of gas concentrations. We used a carbon nanotube array as the first electrode, and the two electric fields between the upper and the lower interelectrode gaps were designed to extract positive ions generated in the upper gap, hence significantly reduced positive ion bombardment on the nanotube electrode, which allowed us to maintain a high electric field near the nanotube tips, leading to a single-valued sensitivity and a long nanotube life. We have demonstrated detection of various gases and simultaneously monitoring temperature, and a potential for applications. PMID:23405281

  16. Effects of Activation Energy to Transient Response of Semiconductor Gas Sensor

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Ohtani, Tatsuki

    The smell classifiable gas sensor will be desired for many applications such as gas detection alarms, process controls for food production and so on. We have tried to realize the sensor using transient responses of semiconductor gas sensor consisting of tin dioxide and pointed out that the sensor gave us different transient responses for kinds of gas. Results of model calculation showed the activation energy of chemical reaction on the sensor surface strongly depended on the transient response. We tried to estimate the activation energies by molecular orbital calculation with SnO2 Cluster. The results show that there is a liner relationship between the gradient of the transient responses and activation energies for carboxylic and alcoholic gases. Transient response will be predicted from activation energy in the same kind of gas and the smell discrimination by single semiconductor gas sensor will be realized by this relationship.

  17. Fault detection, isolation, and diagnosis of status self-validating gas sensor arrays.

    PubMed

    Chen, Yin-Sheng; Xu, Yong-Hui; Yang, Jing-Li; Shi, Zhen; Jiang, Shou-da; Wang, Qi

    2016-04-01

    The traditional gas sensor array has been viewed as a simple apparatus for information acquisition in chemosensory systems. Gas sensor arrays frequently undergo impairments in the form of sensor failures that cause significant deterioration of the performance of previously trained pattern recognition models. Reliability monitoring of gas sensor arrays is a challenging and critical issue in the chemosensory system. Because of its importance, we design and implement a status self-validating gas sensor array prototype to enhance the reliability of its measurements. A novel fault detection, isolation, and diagnosis (FDID) strategy is presented in this paper. The principal component analysis-based multivariate statistical process monitoring model can effectively perform fault detection by using the squared prediction error statistic and can locate the faulty sensor in the gas sensor array by using the variables contribution plot. The signal features of gas sensor arrays for different fault modes are extracted by using ensemble empirical mode decomposition (EEMD) coupled with sample entropy (SampEn). The EEMD is applied to adaptively decompose the original gas sensor signals into a finite number of intrinsic mode functions (IMFs) and a residual. The SampEn values of each IMF and the residual are calculated to reveal the multi-scale intrinsic characteristics of the faulty sensor signals. Sparse representation-based classification is introduced to identify the sensor fault type for the purpose of diagnosing deterioration in the gas sensor array. The performance of the proposed strategy is compared with other different diagnostic approaches, and it is fully evaluated in a real status self-validating gas sensor array experimental system. The experimental results demonstrate that the proposed strategy provides an excellent solution to the FDID of status self-validating gas sensor arrays.

  18. Fault detection, isolation, and diagnosis of status self-validating gas sensor arrays

    NASA Astrophysics Data System (ADS)

    Chen, Yin-sheng; Xu, Yong-hui; Yang, Jing-li; Shi, Zhen; Jiang, Shou-da; Wang, Qi

    2016-04-01

    The traditional gas sensor array has been viewed as a simple apparatus for information acquisition in chemosensory systems. Gas sensor arrays frequently undergo impairments in the form of sensor failures that cause significant deterioration of the performance of previously trained pattern recognition models. Reliability monitoring of gas sensor arrays is a challenging and critical issue in the chemosensory system. Because of its importance, we design and implement a status self-validating gas sensor array prototype to enhance the reliability of its measurements. A novel fault detection, isolation, and diagnosis (FDID) strategy is presented in this paper. The principal component analysis-based multivariate statistical process monitoring model can effectively perform fault detection by using the squared prediction error statistic and can locate the faulty sensor in the gas sensor array by using the variables contribution plot. The signal features of gas sensor arrays for different fault modes are extracted by using ensemble empirical mode decomposition (EEMD) coupled with sample entropy (SampEn). The EEMD is applied to adaptively decompose the original gas sensor signals into a finite number of intrinsic mode functions (IMFs) and a residual. The SampEn values of each IMF and the residual are calculated to reveal the multi-scale intrinsic characteristics of the faulty sensor signals. Sparse representation-based classification is introduced to identify the sensor fault type for the purpose of diagnosing deterioration in the gas sensor array. The performance of the proposed strategy is compared with other different diagnostic approaches, and it is fully evaluated in a real status self-validating gas sensor array experimental system. The experimental results demonstrate that the proposed strategy provides an excellent solution to the FDID of status self-validating gas sensor arrays.

  19. Increasing the selectivity and sensitivity of gas sensors for the detection of explosives

    NASA Astrophysics Data System (ADS)

    Mallin, Daniel

    Over the past decade, the use of improvised explosive devices (IEDs) has increased, domestically and internationally, highlighting a growing need for a method to quickly and reliably detect explosive devices in both military and civilian environments before the explosive can cause damage. Conventional techniques have been successful in explosive detection, however they typically suffer from enormous costs in capital equipment and maintenance, costs in energy consumption, sampling, operational related expenses, and lack of continuous and real-time monitoring. The goal was thus to produce an inexpensive, portable sensor that continuously monitors the environment, quickly detects the presence of explosive compounds and alerts the user. In 2012, here at URI, a sensor design was proposed for the detection of triacetone triperoxide (TATP). The design entailed a thermodynamic gas sensor that measures the heat of decomposition between trace TATP vapor and a metal oxide catalyst film. The sensor was able to detect TATP vapor at the part per million level (ppm) and showed great promise for eventual commercial use, however, the sensor lacked selectivity. Thus, the specific objective of this work was to take the original sensor design proposed in 2012 and to make several key improvements to advance the sensor towards commercialization. It was demonstrated that a sensor can be engineered to detect TATP and ignore the effects of interferent H2O2 molecules by doping SnO2 films with varying amounts of Pd. Compared with a pure SnO2 catalyst, a SnO2, film doped with 8 wt. % Pd had the highest selectivity between TATP and H2O2. Also, at 12 wt. % Pd, the response to TATP and H2O2 was enhanced, indicating that sensitivity, not only selectivity, can be increased by modifying the composition of the catalyst. An orthogonal detection system was demonstrated. The platform consists of two independent sensing mechanisms, one thermodynamic and one conductometric, which take measurements from

  20. Performance and Stress Analysis of Metal Oxide Films for CMOS-Integrated Gas Sensors

    PubMed Central

    Filipovic, Lado; Selberherr, Siegfried

    2015-01-01

    The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250 °C and 550 °C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed. PMID:25815445

  1. A magnonic gas sensor based on magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Matatagui, D.; Kolokoltsev, O. V.; Qureshi, N.; Mejía-Uriarte, E. V.; Saniger, J. M.

    2015-05-01

    In this paper, we propose an innovative, simple and inexpensive gas sensor based on the variation in the magnetic properties of nanoparticles due to their interaction with gases. To measure the nanoparticle response a magnetostatic spin wave (MSW) tunable oscillator has been developed using an yttrium iron garnet (YIG) epitaxial thin film as a delay line (DL). The sensor has been prepared by coating a uniform layer of CuFe2O4 nanoparticles on the YIG film. The unperturbed frequency of the oscillator is determined by a bias magnetic field, which is applied parallel to the YIG film and perpendicularly to the wave propagation direction. In this device, the total bias magnetic field is the superposition of the field of a permanent magnet and the field associated with the layer of magnetic nanoparticles. The perturbation produced in the magnetic properties of the nanoparticle layer due to its interaction with gases induces a frequency shift in the oscillator, allowing the detection of low concentrations of gases. In order to demonstrate the ability of the sensor to detect gases, it has been tested with organic volatile compounds (VOCs) which have harmful effects on human health, such as dimethylformamide, isopropanol and ethanol, or the aromatic hydrocarbons like benzene, toluene and xylene more commonly known by its abbreviation (BTX). All of these were detected with high sensitivity, short response time, and good reproducibility.

  2. A magnonic gas sensor based on magnetic nanoparticles.

    PubMed

    Matatagui, D; Kolokoltsev, O V; Qureshi, N; Mejía-Uriarte, E V; Saniger, J M

    2015-06-07

    In this paper, we propose an innovative, simple and inexpensive gas sensor based on the variation in the magnetic properties of nanoparticles due to their interaction with gases. To measure the nanoparticle response a magnetostatic spin wave (MSW) tunable oscillator has been developed using an yttrium iron garnet (YIG) epitaxial thin film as a delay line (DL). The sensor has been prepared by coating a uniform layer of CuFe2O4 nanoparticles on the YIG film. The unperturbed frequency of the oscillator is determined by a bias magnetic field, which is applied parallel to the YIG film and perpendicularly to the wave propagation direction. In this device, the total bias magnetic field is the superposition of the field of a permanent magnet and the field associated with the layer of magnetic nanoparticles. The perturbation produced in the magnetic properties of the nanoparticle layer due to its interaction with gases induces a frequency shift in the oscillator, allowing the detection of low concentrations of gases. In order to demonstrate the ability of the sensor to detect gases, it has been tested with organic volatile compounds (VOCs) which have harmful effects on human health, such as dimethylformamide, isopropanol and ethanol, or the aromatic hydrocarbons like benzene, toluene and xylene more commonly known by its abbreviation (BTX). All of these were detected with high sensitivity, short response time, and good reproducibility.

  3. Electro-thermal modeling of a microbridge gas sensor

    SciTech Connect

    Manginell, R.P.; Smith, J.H.; Ricco, A.J.; Hughes, R.C.; Moreno, D.J.; Huber, R.J.

    1997-08-01

    Fully CMOS-compatible, surface-micromachined polysilicon microbridges have been designed, fabricated, and tested for use in catalytic, calorimetric gas sensing. To improve sensor behavior, extensive electro-thermal modeling efforts were undertaken using SPICE. The validity of the SPICE model was verified comparing its simulated behavior with experiment. Temperature distribution of an electrically heated microbridges was measured using an infrared microscope. Comparisons among the measured distribution, the SPICE simulation, and distributions obtained by analytical methods show that heating at the ends of a microbridges has important implications for device response. Additional comparisons between measured and simulated current-voltage characteristics, as well as transient response, further support the accuracy of the model. A major benefit of electro- thermal modeling with SPICE is the ability to simultaneously simulate the behavior of a device and its control/sensing electronics. Results for the combination of a unique constant-resistance control circuit and microbridges gas sensor are given. Models of in situ techniques for monitoring catalyst deposition are shown to be in agreement with experiment. Finally, simulated chemical response of the detector is compared with the data, and methods of improving response through modifications in bridge geometry are predicted.

  4. The Development of a Gas-Liquid Two-Phase Flow Sensor Applicable to CBM Wellbore Annulus.

    PubMed

    Wu, Chuan; Wen, Guojun; Han, Lei; Wu, Xiaoming

    2016-11-18

    The measurement of wellbore annulus gas-liquid two-phase flow in CBM (coalbed methane) wells is of great significance for reasonably developing gas drainage and extraction processes, estimating CBM output, judging the operating conditions of CBM wells and analyzing stratum conditions. Hence, a specially designed sensor is urgently needed for real-time measurement of gas-liquid two-phase flow in CBM wellbore annulus. Existing flow sensors fail to meet the requirements of the operating conditions of CBM wellbore annulus due to such factors as an inapplicable measurement principle, larger size, poor sealability, high installation accuracy, and higher requirements for fluid media. Therefore, based on the principle of a target flowmeter, this paper designs a new two-phase flow sensor that can identify and automatically calibrate different flow patterns of two-phase flows. Upon the successful development of the new flow sensor, lab and field tests were carried out, and the results show that the newly designed sensor, with a measurement accuracy of ±2.5%, can adapt to the operating conditions of CBM wells and is reliable for long-term work.

  5. Ag Nanoparticle-Sensitized WO3 Hollow Nanosphere for Localized Surface Plasmon Enhanced Gas Sensors.

    PubMed

    Yao, Yao; Ji, Fangxu; Yin, Mingli; Ren, Xianpei; Ma, Qiang; Yan, Junqing; Liu, Shengzhong Frank

    2016-07-20

    Ag nanoparticle (NP)-sensitized WO3 hollow nanospheres (Ag-WO3-HNSs) are fabricated via a simple sonochemical synthesis route. It is found that the Ag-WO3-HNS shows remarkable performance in gas sensors. Field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images reveal that the Agx-WO3 adopts the HNS structure in which WO3 forms the outer shell framework and the Ag NPs are grown on the inner wall of the WO3 hollow sphere. The size of the Ag NPs can be controlled by adjusting the addition amount of WCl6 during the reaction. The sensor Agx-WO3 exhibits extremely high sensitivity and selectivity toward alcohol vapor. In particular, the Ag(15nm)-WO3 sensor shows significantly lower operating temperature (230 °C), superior detection limits as low as 0.09 ppb, and faster response (7 s). Light illumination was found to boost the sensor performance effectively, especially at 405 and 900 nm, where the light wavelength resonates with the absorption of Ag NPs and the surface oxygen vacancies of WO3, respectively. The improved sensor performance is attributed to the localized surface plasmon resonance (LSPR) effect.

  6. Gas sensor technology at Sandia National Laboratories: Catalytic gate, Surface Acoustic Wave and Fiber Optic Devices

    SciTech Connect

    Hughes, R.C.; Moreno, D.J.; Jenkins, M.W.; Rodriguez, J.L.

    1993-10-01

    Sandia`s gas sensor program encompasses three separate electronic platforms: Acoustic Wave Devices, Fiber Optic Sensors and sensors based on silicon microelectronic devices. A review of most of these activities was presented recently in a article in Science under the title ``Chemical Microsensors.`` The focus of the program has been on understanding and developing the chemical sensor coatings that are necessary for using these electronic platforms as effective chemical sensors.

  7. Sensors and OBIA synergy for operational monitoring of surface water

    NASA Astrophysics Data System (ADS)

    Masson, Eric; Thenard, Lucas

    2010-05-01

    This contribution will focus on combining Object Based Image Analysis (i.e. OBIA with e-Cognition 8) and recent sensors (i.e. Spot 5 XS, Pan and ALOS Prism, Avnir2, Palsar) to address the technical feasibility for an operational monitoring of surface water. Three cases of river meandering (India), flood mapping (Nepal) and dam's seasonal water level monitoring (Morocco) using recent sensors will present various application of surface water monitoring. The operational aspect will be demonstrated either by sensor properties (i.e. spatial resolution and bandwidth), data acquisition properties (i.e. multi sensor, return period and near real-time acquisition) but also with OBIA algorithms (i.e. fusion of multi sensors / multi resolution data and batch processes). In the first case of river meandering (India) we will address multi sensor and multi date satellite acquisition to monitor the river bed mobility within a floodplain using an ALOS dataset. It will demonstrate the possibility of an operational monitoring system that helps the geomorphologist in the analysis of fluvial dynamic and sediment budget for high energy rivers. In the second case of flood mapping (Nepal) we will address near real time Palsar data acquisition at high spatial resolution to monitor and to map a flood extension. This ALOS sensor takes benefit both from SAR and L band properties (i.e. atmospheric transparency, day/night acquisition, low sensibility to surface wind). It's a real achievement compared to optical imagery or even other high resolution SAR properties (i.e. acquisition swath, bandwidth and data price). These advantages meet the operational needs set by crisis management of hydrological disasters but also for the implementation of flood risk management plans. The last case of dam surface water monitoring (Morocco) will address an important issue of water resource management in countries affected by water scarcity. In such countries water users have to cope with over exploitation

  8. Evaluation of an Interferometric Sensor for In-Space Detection of Gas Leaks

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Korman, Valentin; Sinko, John; Hendrickson, Adam

    2009-01-01

    Space mission planning often involves long-term storage of volatile liquids or high-pressure gases. These may include cryogenic fuels and oxidizers, high-pressure gases, and life-support-critical consumables. The risk associated with the storage of fluids and gases in space systems has long been an issue and the ability to retain these fluids is often tied to mission success. A leak in the storage or distribution system can cause many different problems, including a simple, but mission endangering, loss of inventory or, in severe cases, unbalanced thrust loads on a flight vehicle. Cryogenic propellants are especially difficult to store, especially over a long duration. The propellant can boil off and be lost through the insulating walls of the tank or simple thermal cycling of the fittings, valves, and propellant feed lines may unseat seals allowing the fluid to escape. Current NASA missions call for long-duration in-space storage of propellants, oxidizers, and life support supplies. Leaks of a scale detectable through a pressure drop in the storage tank are often catastrophic and have long been the focus of ground-based mitigation efforts where redundant systems are often employed. However, there is presently no technology available for detecting and monitoring low-level, but still mission-endangering, gas leaks in space. Standard in-space gas detection methods either have a very limited pressure range over which they operate effectively or are limited to certain gases. Mass spectrometer systems are able to perform the detection tasks, but their size, mass and use of high voltage, which could potentially lead to an arc that ignites a combustible propellent, severely limit their usefulness in a space system. In this paper, we present results from testing of the light-based interferometric gas monitoring and leak detection sensor shown in Fig. 1. The output of the sensor is an interference fringe pattern that is a function of the gas density, and commensurate index

  9. Selective hydrogen gas sensor using CuFe2O4 nanoparticle based thin film

    NASA Astrophysics Data System (ADS)

    Haija, Mohammad Abu; Ayesh, Ahmad I.; Ahmed, Sadiqa; Katsiotis, Marios S.

    2016-04-01

    Hydrogen gas sensors based on CuFe2O4 nanoparticle thin films are presented in this work. Each gas sensor was prepared by depositing CuFe2O4 thin film on a glass substrate by dc sputtering inside a high vacuum chamber. Argon inert gas was used to sputter the material from a composite sputtering target. Interdigitated metal electrodes were deposited on top of the thin films by thermal evaporation and shadow masking. The produced sensors were tested against hydrogen, hydrogen sulfide, and ethylene gases where they were found to be selective for hydrogen. The sensitivity of the produced sensors was maximum for hydrogen gas at 50 °C. In addition, the produced sensors exhibit linear response signal for hydrogen gas with concentrations up to 5%. Those sensors have potential to be used for industrial applications because of their low power requirement, functionality at low temperatures, and low production cost.

  10. Concept of Operations for Nuclear Warhead Embedded Sensors

    SciTech Connect

    Rockett, P D; Koncher, T R

    2012-05-16

    Embedded arms-control-sensors provide a powerful new paradigm for managing compliance with future nuclear weapons treaties, where deployed warhead numbers will be reduced to 1000 or less. The CONOPS (Concept of Operations) for use with these sensors is a practical tool with which one may help define design parameters, including size, power, resolution, communications, and physical structure. How frequently must data be acquired and must a human be present? Will such data be acquired for only stored weapons or will it be required of deployed weapons as well? Will tactical weapons be subject to such monitoring or will only strategic weapons apply? Which data will be most crucial? Will OSI's be a component of embedded sensor data management or will these sensors stand alone in their data extraction processes? The problem space is massive, but can be constrained by extrapolating to a reasonable future treaty regime and examining the bounded options this scenario poses. Arms control verification sensors, embedded within the warhead case or aeroshell, must provide sufficient but not excessively detailed data, confirming that the item is a nuclear warhead and that it is a particular warhead without revealing sensitive information. Geolocation will be provided by an intermediate transceiver used to acquire the data and to forward the data to a central processing location. Past Chain-of-Custody projects have included such devices and will be primarily responsible for adding such indicators in the future. For the purposes of a treaty regime a TLI will be verified as a nuclear warhead by knowledge of (a) the presence and mass of SNM, (b) the presence of HE, and (c) the reporting of a unique tag ID. All of these parameters can be obtained via neutron correlation measurements, Raman spectroscopy, and fiber optic grating fabrication, respectively. Data from these sensors will be pushed out monthly and acquired nearly daily, providing one of several verification layers in depth

  11. Cross-sensitivity of metal oxide gas sensor to ambient temperature and humidity: Effects on gas distribution mapping

    NASA Astrophysics Data System (ADS)

    Kamarudin, K.; Bennetts, V. H.; Mamduh, S. M.; Visvanathan, R.; Yeon, A. S. A.; Shakaff, A. Y. M.; Zakaria, A.; Abdullah, A. H.; Kamarudin, L. M.

    2017-03-01

    Metal oxide gas sensors have been widely used in robotics application to perform remote and mobile gas sensing. However, previous researches have indicated that this type of sensor technology is cross-sensitive to environmental temperature and humidity. This paper therefore investigates the effects of these two factors towards gas distribution mapping and gas source localization domains. A mobile robot equipped with TGS2600 gas sensor was deployed to build gas distribution maps of indoor environment, where the temperature and humidity varies. The results from the trials in environment with and without gas source indicated that there is a strong relation between the fluctuation of the mean and variance map with respect to the variations in the temperature and humidity maps.

  12. Sensor Data Qualification for Autonomous Operation of Space Systems

    NASA Technical Reports Server (NTRS)

    Maul, William A.; Melcher, Kevin J.; Chicatelli, Amy K.; Sowers, T. Shane

    2006-01-01

    NASA's new Exploration initiative for both robotic and manned missions will require higher levels of reliability, autonomy and reconfiguration capability to make the missions safe, successful and affordable. Future systems will require diagnostic reasoning to assess the health of the system in order to maintain the system s functionality. The diagnostic reasoning and assessment will involve data qualification, fault detection, fault isolation and remediation control. A team of researchers at the NASA Glenn Research Center is currently working on a Sensor Data Qualification (SDQ) system that will support these critical evaluation processes, for both automated and human-in-the-loop applications. Data qualification is required as a first step so that critical safety and operational decisions are based on good data. The SDQ system would monitor a network of related sensors to determine the health of individual sensors within that network. Various diagnostic systems such as the Caution and Warning System would then use the sensor health information with confidence. The proposed SDQ technology will be demonstrated on a variety of subsystems that are relevant to NASA s Exploration systems, which currently include an electrical power system and a cryogenic fluid management system. The focus of this paper is the development and demonstration of a SDQ application for a prototype power distribution unit that is representative of a Crew Exploration Vehicle electrical power system; this provides a unique and relevant environment in which to demonstrate the feasibility of the SDQ technology.

  13. Sensor and tracking data integration into a common operating picture

    NASA Astrophysics Data System (ADS)

    Bailey, Mark E.

    2003-09-01

    With rapid technological developments, a new innovative range of possibilities can be actualized in mainstreaming a network with checks and balances to provide sensor and tracking data integration/information to a wider Department of Defense (DoD) audience or group of agencies. As technologies are developed, methods to display the data are required. Multiple diverse tracking devices and sensors need to be displayed on a common operating picture. Sensors and tracking devices are used to monitor an area or object for movement or boundary penetration. Tracking devices in turn determine transit patterns of humans, animals and/or vehicles. In consortium these devices can have dual applications for military requirements and for other general purposes. The DoD Counterdrug Technology Development Program Office (CDTDPO) has designed a system to distribute sensor and tracking data to multiple users in separate agencies. This information can be displayed in whole or in part as to the specific needs of the user. It is with this purpose that the Data Distribution Network (DDN) was created to disseminate information to a collective group or to a select audience.

  14. Gas sensor based on metal-insulator transition in VO2 nanowire thermistor.

    PubMed

    Strelcov, Evgheni; Lilach, Yigal; Kolmakov, Andrei

    2009-06-01

    Using temperature driven sharp metal-insulator phase transition in single crystal VO(2) nanowires, the realization of a novel gas sensing concept has been tested. Varying the temperature of the nanowire close to the transition edge, the conductance of the nanowire becomes extremely responsive to the tiny changes in molecular composition, pressure, and temperature of the ambient gas environment. This gas sensing analog of the transition edge sensor radiometry used in astrophysics opens new opportunities in gas sensorics.

  15. Mn doped nanostucture ZnO thin film for photo sensor and gas sensor application

    NASA Astrophysics Data System (ADS)

    Mahajan, Sandip V.; Upadhye, Deepak S.; Shaikh, Shahid U.; Birajadar, Ravikiran B.; Siddiqui, Farha Y.; Ghule, Anil V.; Sharma, Ramphal

    2013-02-01

    Mn doped nanostructure ZnO thin film prepared by soft chemically route method. ZnO thin films were deposited on glass substrate by successive ionic layer adsorption and reaction technique (SILAR). After deposit ZnO thin film dipped in MnSO4 solution for 1 min. The optical properties as absorbance were determined using UV-Spectrophotometer and band gap was also calculated. The Structural properties were studied by XRD. The improvement in gas sensing properties was found to enhance after doping of Mn on ZnO thin film. The Photo Sensor nature was calculated by I-V characteristics.

  16. Novel sensors to enable closed-loop active clearance control in gas turbine engines

    NASA Astrophysics Data System (ADS)

    Geisheimer, Jonathan; Holst, Tom

    2014-06-01

    Active clearance control within the turbine section of gas turbine engines presents and opportunity within aerospace and industrial applications to improve operating efficiencies and the life of downstream components. Open loop clearance control is currently employed during the development of all new large core aerospace engines; however, the ability to measure the gap between the blades and the case and close down the clearance further presents as opportunity to gain even greater efficiencies. The turbine area is one of the harshest environments for long term placement of a sensor in addition to the extreme accuracy requirements required to enable closed loop clearance control. This paper gives an overview of the challenges of clearance measurements within the turbine as well as discusses the latest developments of a microwave sensor designed for this application.

  17. Optical Breath Gas Extravehicular Activity Sensor for the Advanced Portable Life Support System

    NASA Technical Reports Server (NTRS)

    Wood, William R.; Casias, Miguel E.; Pilgrim, Jeffrey S.; Chullen, Cinda; Campbell, Colin

    2016-01-01

    The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation portable life support system (PLSS) requires highly accurate CO2 sensing technology with performance beyond that presently in use on the International Space Station extravehicular mobility unit (EMU). Further, that accuracy needs to be provided over the full operating pressure range of the suit (3 to 25 psia). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) sensor based on infrared absorption spectroscopy is being developed for this purpose by Vista Photonics, Inc. Version 1.0 prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The prototypes were upgraded with more sophisticated communications and faster response times to version 2.0 and delivered to JSC in July 2012. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement. The prototypes are controlled digitally with an field-programmable gate array microcontroller architecture. Based on the results of the iterative instrument development, further prototype development and testing of instruments were performed leveraging the lessons learned where feasible. The present development extends and upgrades the earlier hardware for the advanced PLSS 2.5 prototypes for testing at JSC. The prototypes provide significantly enhanced accuracy for water vapor measurement and eliminate wavelength drift affecting the earlier versions. Various improvements to the electronics and gas sampling are currently being advanced including the companion development of engineering development units that will ultimately be capable of radiation tolerance. The combination of low power electronics with the performance of a long wavelength

  18. Tunable Diode Laser Absorption Spectroscopy Sensor for Calibration Free Humidity Measurements in Pure Methane and Low CO2 Natural Gas.

    PubMed

    Nwaboh, Javis Anyangwe; Pratzler, Sonja; Werhahn, Olav; Ebert, Volker

    2016-07-08

    We report a new direct tunable diode laser absorption spectroscopy (dTDLAS) sensor for absolute measurements of H2O in methane, ethane, propane, and low CO2 natural gas. The sensor is operated with a 2.7 µm DFB laser, equipped with a high pressure single pass gas cell, and used to measure H2O amount of substance fractions in the range of 0.31-25 000 µmol/mol. Operating total gas pressures are up to 5000 hPa. The sensor has been characterized, addressing the traceability of the spectrometric results to the SI and the evaluation of the combined uncertainty, following the guide to the expression of uncertainty in measurement (GUM). The relative reproducibility of H2O amount of substance fraction measurements at 87 µmol/mol is 0.26% (0.23 µmol/mol). The maximum precision of the sensor was determined using a H2O in methane mixture, and found to be 40 nmol/mol for a time resolution of 100 s. This corresponds to a normalized detection limit of 330 nmol mol(-1)·m Hz(-1/2) The relative combined uncertainty of H2O amount fraction measurements delivered by the sensor is 1.2%.

  19. Optical-fibre sensor system for monitoring the performance of the gas propellant centrifuge separator of a spacecraft

    NASA Astrophysics Data System (ADS)

    Romo-Medrano, Katya E.; Khotiaintsev, Sergei N.; García-Garduño, Victor

    2004-08-01

    An optical-fibre sensor system is presented for monitoring void fraction distribution in a spacecraft's gas and propellant centrifuge separator. The system could be used at the separator development stage or for monitoring, during ground tests, the elements of the spacecraft propulsion system. Our sensor system employs an array of point optical-fibre refractometric transducers installed in the form of several linear radial arrays on the separator rotating blades. We employed a small-size hemispherical optical detection element as the transducer and we optimized its parameters through numerical ray-tracing. The aim is to minimize the effect of the thin film of liquid that forms on the transducer's surface in this application. The features of this sensor system are: (1) an efficient matrix-type multiplexing scheme, (2) the installation of the main optoelectronic unit of the sensor in a hermetically sealed container inside the separator tank located on the rotating shaft and (3) the spark-proof and explosion-proof design of the sensor circuits and elements. The sensor is simple, reliable, low-cost and is capable of withstanding the factors involved during operation of the propulsion system such as cryogenic temperatures and chemically aggressive liquids. The novel elements and design concepts implemented in this sensor system can also find applications in other sensors for spacecraft propulsion systems and also in a variety of optical-fibre sensors used in scientific research and industry.

  20. Volcano Gas Measurements from UAS - Customization of Sensors and Platforms

    NASA Astrophysics Data System (ADS)

    Werner, C. A.; Dahlgren, R. P.; Kern, C.; Kelly, P. J.; Fladeland, M. M.; Norton, K.; Johnson, M. S.; Sutton, A. J.; Elias, T.

    2015-12-01

    Volcanic eruptions threaten not only the lives and property of local populations, but also aviation worldwide. Volcanic gas release is a key driving force in eruptive activity, and monitoring gas emissions is critical to assessing volcanic hazards, yet most volcanoes are not monitored for volcanic gas emission. Measuring volcanic gas emissions with manned aircraft has been standard practice for many years during eruptive crises, but such measurements are quite costly. As a result, measurements are typically only made every week or two at most during periods of unrest or eruption, whereas eruption dynamics change much more rapidly. Furthermore, very few measurements are made between eruptions to establish baseline emissions. Unmanned aerial system (UAS) measurements of volcanic plumes hold great promise for both improving temporal resolution of measurements during volcanic unrest, and for reducing the exposure of personnel to potentially hazardous conditions. Here we present the results of a new collaborative effort between the US Geological Survey and NASA Ames Research Center to develop a UAS specific for volcano gas monitoring using miniaturized gas sensing systems and a custom airframe. Two miniaturized sensing systems are being built and tested: a microDOAS system to quantify SO2 emission rates, and a miniature MultiGAS system for measuring in-situ concentrations of CO2, SO2, and H2S. The instruments are being built into pods that will be flown on a custom airframe built from surplus Raven RQ-11. The Raven is one of the smallest UAS (a SUAS), and has the potential to support global rapid response when eruptions occur because they require less crew for operations. A test mission is planned for fall 2015 or spring 2016 at the Crows Landing Airfield in central California. Future measurement locations might include Kilauea Volcano in Hawaii, or Pagan Volcano in the Marianas.

  1. Langasite surface acoustic wave gas sensors: modeling and verification

    SciTech Connect

    Peng Zheng,; Greve, D. W.; Oppenheim, I. J.

    2013-03-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  2. Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers

    PubMed Central

    Malagù, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicolò; Zonta, Giulia

    2014-01-01

    Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs) by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC). The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide. PMID:25313496

  3. Gas dependent sensing mechanism in ZnO nanobelt sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Manmeet; Kailasaganapathi, S.; Ramgir, Niranjan; Datta, Niyanta; Kumar, Sushil; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.

    2017-02-01

    Gas sensing properties of ZnO nanobelts synthesized using carbothermal reduction method has been investigated. At room temperature (28 °C), the sensor films exhibit an appreciable response towards H2S and NO and response of these two gases were studied as a function of concentration. For NO the sensor films exhibit a complete reversible curve for the concentration range between 1 and 60 ppm. However, for H2S a complete recovery was obtained for concentration <5 ppm and for higher concentration a partial recovery of the baseline resistance was observed. The reason for the incomplete recovery was investigated using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies of the sample before and after the H2S exposure. After exposure, appearance of an additional peak at 26.6° corresponding to the formation of ZnS was observed in XRD. Formation of additional phase was further corroborated using the results of XPS. H2S exposure causes decrease in the intensity of O 1s peak and appearance of sulphide peaks at binding energies of 162.8 and 161.8 eV corresponding to S-2p peaks - 2p3/2 and 2p1/2, confirms the formation of ZnS upon exposure.

  4. Air Monitoring System in Elders' Apartment with QCM Type Gas Sensors

    NASA Astrophysics Data System (ADS)

    Kikuchi, Masashi; Ito, Tsukasa; Shiratori, Seimei

    The gas monitoring system for elders' apartment using QCM sensors was newly developed. The QCM sensors for sulfide gas and ammonia gas were used for this system. The system for bodily wastes was fabricated and applied to nursing care system in elders' apartment. This system is composed by the sensor unit, communication unit and data server. Care person can see whether the linen should be changed or not without seeing over each room. The QCM sensors have some problems such as the interference of humidity and temperature, therefore these influences were dissolved using humidity sensor and temperature sensor as feedback source. The sensors were placed in several points of elders' apartment for 2 weeks. This system can be used in elders' apartment successfully.

  5. Optical sensors for urban search and rescue operations

    NASA Astrophysics Data System (ADS)

    Mäyrä, Aki P.; Agapiou, Agapios; Hildebrand, Lars; Ojala, Kai M.; Mikedi, Katerina; Statheropoulos, Milt

    2011-11-01

    The Second Generation Locator for Urban Search and Rescue Operations (SGL for USaR) is an EC-funded project solving critical problems following massive destruction and large scale structural collapses in urban locations. One part of the project is the development of a standalone portable first responder device (FIRST) for the operational rescue teams. It will combine field chemical analysis, spectral analysis with audio and video analysis capabilities for the early location of entrapped people, the detection of buried people and air quality monitoring in confined spaces for ensuring safety and security of first responders. Hardware selected for the optical sensors of the FIRST-device will be responsible for the fluorescence, visible (VIS), near infrared (NIR) and long wavelength infrared (LWIR) range detection as well as supplying required illumination. FIRST shall identify images of fires or other events, damage patterns, temperature of living humans, motion of body parts and human postures. The device requirements were based on the operational input and feedback received from European rescue teams - partners within the project (final product end-users). Some of the critical properties for the selected components were compact physical size, low power consumption, refresh rate and adequate resolution of the sensor image data. During the project, special image libraries were collected and suitable image processing algorithms based on the collected data were developed.

  6. Gas pipeline adjusts operations to meet Order 636

    SciTech Connect

    Cummins, J.D. )

    1994-04-18

    Responding to US Federal Energy Regulatory Commission's Order 636, Texas Gas Transmission Corp., Owensboro, Ky., has instituted an allocation procedure for unbundled supply, pipeline transportation, and storage while maintaining system security and providing required services to each customer. FERC Order 636 requires federally regulated natural-gas pipelines to separate, or unbundle,' such traditional sales services as supply, transportation, and storage. Formerly, these services could be offered as a package, an arrangement the commission felt discouraged competition. Because Texas Gas has always relied heavily on bundled operation to provide efficient service to end users, the order has profoundly affected projected design and operational strategies. The greatest challenge has been to maintain or exceed current levels of safety, reliability, and efficiency. The paper describes the Texas Gas system, allocation, developing profiles, supply-area operation, and an example of the method used by Texas Gas.

  7. Sensor Data Qualification Technique Applied to Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Simon, Donald L.

    2013-01-01

    This paper applies a previously developed sensor data qualification technique to a commercial aircraft engine simulation known as the Commercial Modular Aero-Propulsion System Simulation 40,000 (C-MAPSS40k). The sensor data qualification technique is designed to detect, isolate, and accommodate faulty sensor measurements. It features sensor networks, which group various sensors together and relies on an empirically derived analytical model to relate the sensor measurements. Relationships between all member sensors of the network are analyzed to detect and isolate any faulty sensor within the network.

  8. Placement of sensors in operational modal analysis for truss bridges

    NASA Astrophysics Data System (ADS)

    Debnath, N.; Dutta, A.; Deb, S. K.

    2012-08-01

    A modal approach is considered for sensor placement evaluation in operational modal analysis (OMA) where modal participation at individual degree of freedom (DOF) is evaluated separately for the target modes and subsequently locations are identified using these participation profiles. Modal contribution in output energy (MCOE) is proposed as modal measure to evaluate modal participation and has been applied in this modal approach framework for sensor placement evaluation. MCOE is evaluated using observability grammian for any types of response measurement (displacement, velocity or acceleration), while a system is released from any initial condition. Further, existing modal measures e.g. modal Hankel singular value (MHSV) and system norms (H2, H∞ and Hankel) are explained in perspective of OMA. To understand the efficiency of this proposed technique, MCOE is compared in terms of modal participation with existing modal measures as well as with other techniques like effective independence (EI) and modal kinetic energy (MKE). Analytical similarity is found for participation of a mode with EI method. Further, an existing large truss bridge structure is considered for comparative study based on modal participation of individual target modes along each DOF with acceleration measurement. In this comparison, MCOE technique is found to be in very good agreement with EI method as expected, while good agreement is observed with MHSV as well as norms and reasonable agreement with MKE method. Further, the adopted modal approach uses a flexible and insightful methodology for sensor location evaluation for multiple target modes.

  9. Readout Circuit System for In2O3/RGO Nanocomposite Gas Sensors

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Yi

    A readout circuit system for In2O3/RGO nanocomposite gas sensors using open-source software has been developed for the first time. The readout system adopts a Raspberry Pi as an electronic control unit and incorporates different electronics components to realize the function of a source measure unit (SMU). During the operation, real-time results of measured gas concentrations can be accessed through the Internet and alarm functions are also included. All control programs were written in Python language. Using this readout system, current response of gas sensors toward oxygen concentrations (2,000---32,000 ppm) in argon environment at 140 °C are in a good agreement with the data measured by Agilent SMU (B2902A). Furthermore, temperature effects and transient response of the proposed system are investigated. The success of this readout system demonstrates the potential use of open-source hardware to construct scientific instruments with the advantages of miniaturization, low cost, flexible design, and Internet access.

  10. 13CO2/12CO2 isotopic ratio measurements using a difference frequency-based sensor operating at 4.35 micrometers

    NASA Technical Reports Server (NTRS)

    Erdelyi, M.; Richter, D.; Tittel, F. K.

    2002-01-01

    A portable modular gas sensor for measuring the 13C/12C isotopic ratio in CO2 with a precision of 0.8%(+/-1 sigma) was developed for volcanic gas emission studies. This sensor employed a difference frequency generation (DFG)-based spectroscopic source operating at 4.35 micrometers (approximately 2300 cm-1) in combination with a dual-chamber gas absorption cell. Direct absorption spectroscopy using this specially designed cell permitted rapid comparisons of isotopic ratios of a gas sample and a reference standard for appropriately selected CO2 absorption lines. Special attention was given to minimizing undesirable precision degrading effects, in particular temperature and pressure fluctuations.

  11. In2O3-based micro gas sensor for detecting NO x gases

    NASA Astrophysics Data System (ADS)

    Kim, Bum-Joon; Song, In-Gyu; Kim, Jung-Sik

    2014-03-01

    In this study, NO x micro gas sensors for monitoring the indoor atmosphere of automobile were fabricated using MEMS (microelectromechanical system) technology and a sol-gel process. The sensing electrode and micro heater were designed to have a co-planar typed structure in a Pt thin film layer. The thermal characteristics of a micro heater array were analyzed using a finite element method (FEM). The chip size of the gas sensor was approximately 2 mm × 2 mm. Indium oxide as a sensing material for NO x gas was synthesized by a sol-gel process with indium isopropoxide as a precursor. Field emission Scanning electron microscopy and x-ray diffraction showed that particle size of the synthesized In2O3 was approximately 17-45 nm. The maximum gas sensitivity as the relative resistance ( R s = R gas / R air ) was observed at 275°C with a value of 8.0 at 1 ppm NO2 gas. The response (80% saturation) and recovery times were within 1 min. The sensing properties of NO2 gas exhibited linear behavior with increasing gas concentration. The sensing mechanism of the gas sensor was explained by the variations in the electron depletion layers and the adsorption of gas molecules on the In2O3 particle surface. These results suggest that in the future, MEMS-based gas sensors can be used as automotive-exhaust-gas sensors.

  12. Compact Laser-Based Sensors for Monitoring and Control of Gas Turbine Combustors

    NASA Technical Reports Server (NTRS)

    Hanson, Ronald K.; Jeffries, Jay B.

    2003-01-01

    Research is reported on the development of sensors for gas turbine combustor applications that measure real-time gas temperature using near-infrared water vapor absorption and concentration in the combustor exhaust of trace quantities of pollutant NO and CO using mid-infrared absorption. Gas temperature is extracted from the relative absorption strength of two near-infrared transitions of water vapor. From a survey of the water vapor absorption spectrum, two overtone transitions near 1800 nm were selected that can be rapidly scanned in wavelength by injection current tuning a single DFB diode laser. From the ratio of the absorbances on these selected transitions, a path-integrated gas temperature can be extracted in near-real time. Demonstration measurements with this new temperature sensor showed that combustor instabilities could be identified in the power spectrum of the temperature versus time record. These results suggest that this strategy is extremely promising for gas turbine combustor control applications. Measurements of the concentration of NO and CO in the combustor exhaust are demonstrated with mid-infrared transitions using thermo-electrically cooled, quantum cascade lasers operating near 5.26 and 4.62 microns respectively. Measurements of NO are performed in an insulated exhaust duct of a C2H4-air flame at temperatures of approximately 600 K. CO measurements are performed above a rich H2-air flame seeded with CO2 and cooled with excess N2 to 1150 K. Using a balanced ratiometric detection technique a sensitivity of 0.36 ppm-m was achieved for NO and 0.21 ppm-m for CO. Comparisons between measured and predicted water-vapor and CO2 interference are discussed. The mid-infrared laser quantum cascade laser technology is in its infancy; however, these measurements demonstrate the potential for pollutant monitoring in exhaust gases with mid-IR laser absorption.

  13. Titanium dioxide-based carbon monoxide gas sensors: Effects of crystallinity and chemistry on sensitivity

    NASA Astrophysics Data System (ADS)

    Seeley, Zachary Mark

    Among metal-oxide gas sensors which change electrical resistive properties upon exposure to target gasses, titanium dioxide (TiO2) has received attention for its sensitivity and stability during high temperature (>500°C) operation. However, due to the sensing mechanism sensitivity, selectivity, and stability remain as critical deficiencies to be resolved before these sensors reach commercial use. In this study, TiO2 thick films of approximately 30mum and thin films of approximately 1mum thick were fabricated to assess the influence of their material properties on gas sensing mechanism. Increased calcination temperature of TiO2 thick films led to grain growth, reduction in specific surface area, and particle-particle necking. These properties are known to degrade sensitivity; however the measured carbon monoxide (CO) gas response improved with increasing calcination temperature up to 800°C. It was concluded that the sensing improvement was due to increased crystallinity within the films. Sensing properties of TiO2 thin films of were also dependent on crystallization, however; due to the smaller volume of material, they reached optimized crystallization at lower temperatures of 650°C, compared to 800°C for thick films. Incorporation of tungsten (W) and nickel (Ni) ions into the films created donor and acceptor defect sites, respectively, within the electronic band gap of TiO2. The additional n-type defects in W-doped TiO 2 improved n-type CO response, while p-type defects in Ni-doped TiO 2 converted the gas response to p-type. Chemistry of thin films had a more significant impact on the electrical properties and gas response than did microstructure or crystallinity. Doped films could be calcined at higher temperatures and yet remain highly sensitive to CO. Thin films with p-n bi-layer structure were fabricated to determine the influence of a p-n junction on gas sensing properties. No effect of the junction was observed and the sensing response neared the average

  14. Algebraic operator approach to gas kinetic models

    NASA Astrophysics Data System (ADS)

    Il'ichov, L. V.

    1997-02-01

    Some general properties of the linear Boltzmann kinetic equation are used to present it in the form ∂ tϕ = - †Âϕ with the operators Âand† possessing some nontrivial algebraic properties. When applied to the Keilson-Storer kinetic model, this method gives an example of quantum ( q-deformed) Lie algebra. This approach provides also a natural generalization of the “kangaroo model”.

  15. Surface functionalization by gold nanoparticles and its prospects for application in conductometric metal oxide gas sensors

    NASA Astrophysics Data System (ADS)

    Korotcenkov, G.; Brinzari, V.; Cho, B. K.

    2017-03-01

    Approaches to surface functionalizing by gold nanoparticles of metal oxides aimed for gas sensors applications are discussed in this paper. It is demonstrated that surface modification by gold nanoparticles is accompanied by improvement of sensor performance. However, analysis of obtained results has shown that the achievement of strong improvement of gas sensor parameters is not a trivial task. For its reduction, it is necessary to ensure several specific conditions related to the size and density of gold clusters on the surface of metal oxide crystallites, the state of gold in the cluster, and to the properties of the metal oxide support used. It is also demonstrated that additional studies are required before conductometric gas sensors modified by gold nanoclusters will appear in gas-sensor market.

  16. Solid State Gas Sensor Research in Germany – a Status Report

    PubMed Central

    Moos, Ralf; Sahner, Kathy; Fleischer, Maximilian; Guth, Ulrich; Barsan, Nicolae; Weimar, Udo

    2009-01-01

    This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor. PMID:22408529

  17. A computational chemist approach to gas sensors: modeling the response of SnO2 to CO, O2, and H2O gases.

    PubMed

    Ducéré, Jean-Marie; Hemeryck, Anne; Estève, Alain; Rouhani, Mehdi Djafari; Landa, Georges; Ménini, Philippe; Tropis, Cyril; Maisonnat, André; Fau, Pierre; Chaudret, Bruno

    2012-01-30

    A general bottom-up modeling strategy for gas sensor response to CO, O(2), H(2)O, and related mixtures exposure is demonstrated. In a first stage, we present first principles calculations that aimed at giving an unprecedented review of basic chemical mechanisms taking place at the sensor surface. Then, simulations of an operating gas sensor are performed via a mesoscopic model derived from calculated density functional theory data into a set of differential equations. Significant presence of catalytic oxidation reaction is highlighted.

  18. FUEL CELL OPERATION ON LANDFILL GAS AT PENROSE POWER STATION

    EPA Science Inventory

    This demonstration test successfully demonstrated operation of a commercial phosphoric acid fuel cell (FC) on landfill gas (LG) at the Penrose Power Station in Sun Valley, CA. Demonstration output included operation up to 137 kW; 37.1% efficiency at 120 kW; exceptionally low sec...

  19. PCF-Based Cavity Enhanced Spectroscopic Sensors for Simultaneous Multicomponent Trace Gas Analysis

    PubMed Central

    Nakaema, Walter M.; Hao, Zuo-Qiang; Rohwetter, Philipp; Wöste, Ludger; Stelmaszczyk, Kamil

    2011-01-01

    A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + δ) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a “quasi continuum” mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given. PMID:22319372

  20. Analyzer for measurement of nitrogen oxide concentration by ozone content reduction in gas using solid state chemiluminescent sensor

    NASA Astrophysics Data System (ADS)

    Chelibanov, V. P.; Ishanin, G. G.; Isaev, L. N.

    2014-05-01

    Role of nitrogen oxide in ambient air is described and analyzed. New method of nitrogen oxide concentration measurement in gas phase is suggested based on ozone concentration measurement with titration by nitrogen oxide. Research of chemiluminescent sensor composition is carried out on experimental stand. The sensor produced on the base of solid state non-activated chemiluminescent composition is applied as ozone sensor. Composition is put on the surface of polymer matrix with developed surface. Sensor compositions includes gallic acid with addition of rodamine-6G. Model of interaction process between sensor composition and ozone has been developed, main products appeared during reaction are identified. The product determining the speed of luminescense appearance is found. This product belongs to quinone class. Then new structure of chemiluminescent composition was suggested, with absence of activation period and with high stability of operation. Experimental model of gas analyzer was constructed and operation algorithm was developed. It was demonstrated that developed NO measuring instrument would be applied for monitoring purposes of ambient air. This work was partially financially supported by Government of Russian Federation, Grant 074-U01

  1. 76 FR 21395 - BOEMRE Information Collection Activity; 1010-0141, Subpart D, Oil and Gas Drilling Operations...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-15

    ... lease. Operations on the OCS must preserve, protect, and develop oil and natural gas resources in a... signs and use other visual and audible systems. 490(j)(7-8) Test H2S detection and 4. monitoring sensors during drilling; record testing and calibrations on occasion, daily during drilling (approx. 12...

  2. Investigation of Gas-Sensing Property of Acid-Deposited Polyaniline Thin-Film Sensors for Detecting H₂S and SO₂.

    PubMed

    Dong, Xingchen; Zhang, Xiaoxing; Wu, Xiaoqing; Cui, Hao; Chen, Dachang

    2016-11-10

    Latent insulation defects introduced in manufacturing process of gas-insulated switchgears can lead to partial discharge during long-time operation, even to insulation fault if partial discharge develops further. Monitoring of decomposed components of SF₆, insulating medium of gas-insulated switchgear, is a feasible method of early-warning to avoid the occurrence of sudden fault. Polyaniline thin-film with protonic acid deposited possesses wide application prospects in the gas-sensing field. Polyaniline thin-film sensors with only sulfosalicylic acid deposited and with both hydrochloric acid and sulfosalicylic acid deposited were prepared by chemical oxidative polymerization method. Gas-sensing experiment was carried out to test properties of new sensors when exposed to H₂S and SO₂, two decomposed products of SF₆ under discharge. The gas-sensing properties of these two sensors were compared with that of a hydrochloric acid deposited sensor. Results show that the hydrochloric acid and sulfosalicylic acid deposited polyaniline thin-film sensor shows the most outstanding sensitivity and selectivity to H₂S and SO₂ when concentration of gases range from 10 to 100 μL/L, with sensitivity changing linearly with concentration of gases. The sensor also possesses excellent long-time and thermal stability. This research lays the foundation for preparing practical gas-sensing devices to detect H₂S and SO₂ in gas-insulated switchgears at room temperature.

  3. Investigation of Gas-Sensing Property of Acid-Deposited Polyaniline Thin-Film Sensors for Detecting H2S and SO2

    PubMed Central

    Dong, Xingchen; Zhang, Xiaoxing; Wu, Xiaoqing; Cui, Hao; Chen, Dachang

    2016-01-01

    Latent insulation defects introduced in manufacturing process of gas-insulated switchgears can lead to partial discharge during long-time operation, even to insulation fault if partial discharge develops further. Monitoring of decomposed components of SF6, insulating medium of gas-insulated switchgear, is a feasible method of early-warning to avoid the occurrence of sudden fault. Polyaniline thin-film with protonic acid deposited possesses wide application prospects in the gas-sensing field. Polyaniline thin-film sensors with only sulfosalicylic acid deposited and with both hydrochloric acid and sulfosalicylic acid deposited were prepared by chemical oxidative polymerization method. Gas-sensing experiment was carried out to test properties of new sensors when exposed to H2S and SO2, two decomposed products of SF6 under discharge. The gas-sensing properties of these two sensors were compared with that of a hydrochloric acid deposited sensor. Results show that the hydrochloric acid and sulfosalicylic acid deposited polyaniline thin-film sensor shows the most outstanding sensitivity and selectivity to H2S and SO2 when concentration of gases range from 10 to 100 μL/L, with sensitivity changing linearly with concentration of gases. The sensor also possesses excellent long-time and thermal stability. This research lays the foundation for preparing practical gas-sensing devices to detect H2S and SO2 in gas-insulated switchgears at room temperature. PMID:27834895

  4. Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices

    PubMed Central

    Anderson, Travis; Ren, Fan; Pearton, Stephen; Kang, Byoung Sam; Wang, Hung-Ta; Chang, Chih-Yang; Lin, Jenshan

    2009-01-01

    In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO2 and C2H4 using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application. PMID:22408548

  5. Development of micro-heaters with optimized temperature compensation design for gas sensors.

    PubMed

    Hwang, Woo-Jin; Shin, Kyu-Sik; Roh, Ji-Hyoung; Lee, Dae-Sung; Choa, Sung-Hoon

    2011-01-01

    One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20 ms, indicating a very high efficiency of pulse driving.

  6. Novel Gas Sensor Based on ZnO Nanorod Circular Arrays for C2H5OH Gas Detection.

    PubMed

    Jianjiao, Zhang; Hongyan, Yue; Erjun, Guo; Shaolin, Zhang; Liping, Wang; Chunyu, Zhang; Xin, Gao; Jing, Chang; Hong, Zhang

    2015-03-01

    Novel side-heating gas sensor based on ZnO nanorod circular arrays was firstly fabricated by hydrothermal treatment assisted with a kind of simple dip-coating technique. The structure and morphologies of ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), respectively. XRD result indicates that the obtained ZnO nanorods have good crystalline with the hexagonal wurtzite structure. SEM result indicates that ZnO nanorod arrays are vertically growth on the surface of ceramic tube of side-heating sensor with controlled diameter and length, narrow size distribution and high orientation. The gas sensing properties of ZnO nanorod circular arrays are also evaluated. Comparative to the sensor based on scattered ZnO nanorods responding to 25 ppm H2, CO, C6H5CH3 and C2H5OH gas, respectively, the sensing values of high orientation gas sensor are generally increased by 5%. This novel sensor has good application promising for the fabrication of cost effective and high performance gas sensors.

  7. Development of an Acoustic Sensor On-Line Gas Temperature Measurement in Gasifiers

    SciTech Connect

    Peter Ariessohn

    2008-06-30

    This project was awarded under U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) Program Solicitation DE-PS26-02NT41422 and specifically addresses Technical Topical Area 2 - Gasification Technologies. The project team includes Enertechnix, Inc. as the main contractor and ConocoPhillips Company as a technical partner, who also provides access to the SG Solutions Gasification Facility (formerly Wabash River Energy Limited), host for the field-testing portion of the research. The objective of this project was to adapt acoustic pyrometer technology to make it suitable for measuring gas temperature inside a coal gasifier, to develop a prototype sensor based on this technology, and to demonstrate its performance through testing on a commercial gasifier. The project was organized in three phases, each of approximately one year duration. The first phase consisted of researching a variety of sound generation and coupling approaches suitable for use with a high pressure process, evaluation of the impact of gas composition variability on the acoustic temperature measurement approach, evaluation of the impact of suspended particles and gas properties on sound attenuation, evaluation of slagging issues and development of concepts to deal with this issue, development and testing of key prototype components to allow selection of the best approaches, and development of a conceptual design for a field prototype sensor that could be tested on an operating gasifier. The second phase consisted of designing and fabricating a series of prototype sensors, testing them in the laboratory, and developing a conceptual design for a field prototype sensor. The third phase consisted of designing and fabricating the field prototype, and testing it in the lab and in a commercial gasifier to demonstrate the ability to obtain accurate measurements of gas temperature in an operating gasifier. Following the completion of the initial 3 year project, several continuations

  8. Optimization of wastewater treatment plant operation for greenhouse gas mitigation.

    PubMed

    Kim, Dongwook; Bowen, James D; Ozelkan, Ertunga C

    2015-11-01

    This study deals with the determination of optimal operation of a wastewater treatment system for minimizing greenhouse gas emissions, operating costs, and pollution loads in the effluent. To do this, an integrated performance index that includes three objectives was established to assess system performance. The ASMN_G model was used to perform system optimization aimed at determining a set of operational parameters that can satisfy three different objectives. The complex nonlinear optimization problem was simulated using the Nelder-Mead Simplex optimization algorithm. A sensitivity analysis was performed to identify influential operational parameters on system performance. The results obtained from the optimization simulations for six scenarios demonstrated that there are apparent trade-offs among the three conflicting objectives. The best optimized system simultaneously reduced greenhouse gas emissions by 31%, reduced operating cost by 11%, and improved effluent quality by 2% compared to the base case operation.

  9. Development of harsh environment nitrogen oxides solid-state gas sensors

    NASA Astrophysics Data System (ADS)

    Szabo, Nicholas Frank

    The goal of this dissertation was to study and develop high temperature solid-state sensors for combustion based gases. Specific attention was focused on NOx gases (NO and NO2) as they are of significant importance with respect to the environment and the health of living beings. This work is divided into four sections with the first chapter being an introduction into the effects of NOx gases and current regulations, followed by an introduction to the field of high temperature NOx sensors and finally where and why they will be needed in the future. Chapter 2 focuses on the development of a gas sensor for NOx capable of operation in harsh environments. The basis of the sensor is a mixed potential response at 500/600°C generated by exposure of gases to a platinum-yttria stabilized zirconia (Pt-YSZ) interface. Asymmetry between the two Pt electrodes on YSZ is generated by covering one of the electrodes with a zeolite, which helps to bring NO/NO2 towards equilibrium prior to the gases reaching the electrochemically active interface. Three sensor designs have been examined, including a planar design that is amenable to packaging for surviving automotive exhaust streams. Automotive tests indicated that the sensor is capable of detecting NO in engine exhausts. Chapter 2 concluded that it is difficult to measure NO or NO2 selectively especially when both gases are present at the same time thus we have developed a strategy in chapter 3 to measure the total NOx level (NO + NO2) in a background of O2 and N2 at high temperatures with minimal CO interference by combining a catalytic filter bed with the existing YSZ sensor device. The filter bed was composed of a Pt catalyst dispersed onto a zeolite Y support placed before a YSZ sensor having an air reference with a Cr2O3 or Pt sensing electrode. Chapter 4 explores the reasons for the difference in sensitivity of metal oxide electrodes, Cr2O3 and a mixed conducting perovskite La0.6Sr0.4Fe0.8Co0.2Ox, with the goal of ultimately

  10. Metal-oxide-semiconductor based gas sensors: screening, preparation, and integration.

    PubMed

    Zhang, Jian; Qin, Ziyu; Zeng, Dawen; Xie, Changsheng

    2017-03-01

    Metal-oxide-semiconductor (MOS) based gas sensors have been considered a promising candidate for gas detection over the past few years. However, the sensing properties of MOS-based gas sensors also need to be further enhanced to satisfy the higher requirements for specific applications, such as medical diagnosis based on human breath, gas detection in harsh environments, etc. In these fields, excellent selectivity, low power consumption, a fast response/recovery rate, low humidity dependence and a low limit of detection concentration should be fulfilled simultaneously, which pose great challenges to the MOS-based gas sensors. Recently, in order to improve the sensing performances of MOS-based gas sensors, more and more researchers have carried out extensive research from theory to practice. For a similar purpose, on the basis of the whole fabrication process of gas sensors, this review gives a presentation of the important role of screening and the recent developments in high throughput screening. Subsequently, together with the sensing mechanism, the factors influencing the sensing properties of MOSs involved in material preparation processes were also discussed in detail. It was concluded that the sensing properties of MOSs not only depend on the morphological structure (particle size, morphology, pore size, etc.), but also rely on the defect structure and heterointerface structure (grain boundaries, heterointerfaces, defect concentrations, etc.). Therefore, the material-sensor integration was also introduced to maintain the structural stability in the sensor fabrication process, ensuring the sensing stability of MOS-based gas sensors. Finally, the perspectives of the MOS-based gas sensors in the aspects of fundamental research and the improvements in the sensing properties are pointed out.

  11. The effect of ultraviolet irradiation on the ultra-thin HfO{sub 2} based CO gas sensor

    SciTech Connect

    Karaduman, Irmak; Barin, Özlem; Acar, Selim; Yıldız, Dilber Esra

    2015-11-07

    In this work, an effort has been made to fabricate ultrathin HfO{sub 2}/Al{sub 2}O{sub 3} sample by atomic layer deposition method for the fast detection of CO gas at room temperature. The effect of the operating temperature and the UV light on the gas sensing characteristics has been studied. We investigated the optimum operating temperature for the sample by sensing 25 ppm CO and CO{sub 2} gases from room temperature to 150 °C for 10 °C steps. The maximum response was obtained at 150 °C for both gases in the measurement temperature range. Also, the photoresponse measurements clearly show the effect of UV light on the sample. At room temperature, sensor showed superior response (14%) for 5 ppm CO gas. The response time of sensor is 6 s to 5 ppm CO gas concentration. The ultrathin HfO{sub 2} based sample shows acceptable gas sensitivity for 5 ppm CO gas at room temperature under UV light irradiation.

  12. An electromagnetic cavity sensor for multiphase measurement in the oil and gas industry

    NASA Astrophysics Data System (ADS)

    Al-Hajeri, S.; Wylie, S. R.; Stuart, R. A.; Al-Shamma'a, A. I.

    2007-07-01

    The oil and gas industry require accurate sensors to monitor fluid flow in pipelines in order to manage wells efficiently. The sensor described in this paper uses the different relative permittivity values for the three phases: oil, gas and water to help determine the fraction of each phase in the pipeline, by monitoring the resonant frequencies that occur within an electromagnetic cavity. The sensor has been designed to be non-intrusive. This is advantageous, as it will prevent the sensor being damaged by the flow through the pipeline and allow pigging, the technique used for cleaning rust and wax from the inside of the pipeline using blades or brushes.

  13. Gas sensors based on polyaniline/zinc oxide hybrid film for ammonia detection at room temperature

    NASA Astrophysics Data System (ADS)

    Zhu, Guotao; Zhang, Qiuping; Xie, Guangzhong; Su, Yuanjie; Zhao, Kang; Du, Hongfei; Jiang, Yadong

    2016-11-01

    Polyaniline/zinc oxide (PANI/ZnO) hybrid film based sensors have been developed for ammonia (NH3) detection at room temperature (RT). Results shows that hybrid film sensor exhibits a p-type semiconductor behavior and larger response than that of pure PANI film sensor. In the system, ZnO nanorod arrays can not only create nanoscale gap for gas diffusion but also provide abundant adsorption sites, thus leading to enhancement of response. Besides, hydrothermal time is proportional to the length of nanorods, Longer nanorods will provide efficient gap for gas diffusion, which leads to better sensitivity. This work offers a promising way to optimize sensor performance.

  14. Operating Experience Review of the INL HTE Gas Monitoring System

    SciTech Connect

    L. C. Cadwallader; K. G. DeWall

    2010-06-01

    This paper describes the operations of several types of gas monitors in use at the Idaho National Laboratory (INL) High Temperature Electrolysis Experiment (HTE) laboratory. The gases monitored at hydrogen, carbon monoxide, carbon dioxide, and oxygen. The operating time, calibration, and unwanted alarms are described. The calibration session time durations are described. Some simple statistics are given for the reliability of these monitors and the results are compared to operating experiences of other types of monitors.

  15. Carbon dioxide gas sensor derived from a 547-hole microstructured polymer optical fiber preform.

    PubMed

    Wang, Jian; Wang, Lili

    2010-10-01

    In this Letter, we report a carbon dioxide gas sensor having 547 pieces of thin-film modified capillaries, which are derived from a microstructured polymer optical fiber preform. Compared with the conventional absorption-based sensor, the monolithic polymer capillary waveguide arrays have better sensitivity, because the huge sensing surfaces, composed of 547 pieces of dye-indicator-doped porous ethyl cellulose layers, interact directly with the gas molecules. As far as we know, a gas sensor based on multichannel capillary waveguide arrays has not been reported before.

  16. A Novel Solid State Non-Dispersive Infrared CO2 Gas Sensor Compatible with Wireless and Portable Deployment

    PubMed Central

    Gibson, Desmond; MacGregor, Calum

    2013-01-01

    This paper describes development of a novel mid-infrared light emitting diode (LED) and photodiode (PD) light source/detector combination and use within a non-dispersive infrared (NDIR) carbon dioxide gas sensor. The LED/PD based NDIR sensor provides fast stabilisation time (time required to turn on the sensor from cold, warm up, take and report a measurement, and power down again ≈1 second), longevity (>15 years), low power consumption and low cost. Described performance is compatible with “fit and forget” wireless deployed sensors in applications such as indoor air quality monitoring/control & energy conservation in buildings, transport systems, horticultural greenhouses and portable deployment for safety, industrial and medical applications. Fast stabilisation time, low intrinsic power consumption and cycled operation offer typical energy consumption per measurement of mJ's, providing extended operation using battery and/or energy harvesting strategies (measurement interval of ≈ 2 minutes provides >10 years operation from one AA battery). Specific performance data is provided in relation to measurement accuracy and noise, temperature performance, cross sensitivity, measurement range (two pathlength variants are described covering ambient through to 100% gas concentration), comparison with NDIR utilizing thermal source/pyroelectric light source/detector combination and compatibility with energy harvesting. Semiconductor based LED/PD processing together with injection moulded reflective optics and simple assembly provide a route to low cost high volume manufacturing. PMID:23760090

  17. A novel solid state non-dispersive infrared CO2 gas sensor compatible with wireless and portable deployment.

    PubMed

    Gibson, Desmond; MacGregor, Calum

    2013-05-29

    This paper describes development of a novel mid-infrared light emitting diode (LED) and photodiode (PD) light source/detector combination and use within a non-dispersive infrared (NDIR) carbon dioxide gas sensor. The LED/PD based NDIR sensor provides fast stabilisation time (time required to turn on the sensor from cold, warm up, take and report a measurement, and power down again ≈1 second), longevity (>15 years), low power consumption and low cost. Described performance is compatible with "fit and forget" wireless deployed sensors in applications such as indoor air quality monitoring/control & energy conservation in buildings, transport systems, horticultural greenhouses and portable deployment for safety, industrial and medical applications. Fast stabilisation time, low intrinsic power consumption and cycled operation offer typical energy consumption per measurement of mJ's, providing extended operation using battery and/or energy harvesting strategies (measurement interval of ≈ 2 minutes provides >10 years operation from one AA battery). Specific performance data is provided in relation to measurement accuracy and noise, temperature performance, cross sensitivity, measurement range (two pathlength variants are described covering ambient through to 100% gas concentration), comparison with NDIR utilizing thermal source/pyroelectric light source/detector combination and compatibility with energy harvesting. Semiconductor based LED/PD processing together with injection moulded reflective optics and simple assembly provide a route to low cost high volume manufacturing.

  18. Imaging the operation of a carbon nanotube charge sensor at the nanoscale.

    PubMed

    Brunel, David; Mayer, Alexandre; Mélin, Thierry

    2010-10-26

    Carbon nanotube field effect transistors (CNTFETs) are of great interest for nanoelectronics applications such as nonvolatile memory elements (NVMEs) or charge sensors. In this work, we use a scanning-probe approach based on a local charge perturbation of CNTFET-based NVMEs and investigate their fundamental operation from combined transport, electrostatic scanning probe techniques and atomistic simulations. We experimentally demonstrate operating devices with threshold voltages shifts opposite to conventional gating and with almost unchanged hysteresis. The former effect is quantitatively understood as the emission of a delocalized image charge pattern in the nanotube environment, in response to local charge storage, while the latter effect points out the dominant dipolar nature of hysteresis in CNTFETs. We propose a simple model for charge sensing using CNTFETs, based on the redistribution of the nanotube image charges. This model could be extended to gas or biosensing, for example.

  19. Sensor for performance monitoring of advanced gas turbines

    NASA Astrophysics Data System (ADS)

    Latvakoski, Harri M.; Markham, James R.; Harrington, James A.; Haan, David J.

    1999-01-01

    Advanced thermal coating materials are being developed for use in the combustor section of high performance turbine engines to allow for higher combustion temperatures. To optimize the use of these thermal barrier coatings (TBC), accurate surface temperature measurements are required to understand their response to changes in the combustion environment. Present temperature sensors, which are based on the measurement of emitted radiation, are not well studied for coated turbine blades since their operational wavelengths are not optimized for the radiative properties of the TBC. This work is concerned with developing an instrument to provide accurate, real-time measurements of the temperature of TBC blades in an advanced turbine engine. The instrument will determine the temperature form a measurement of the radiation emitted at the optimum wavelength, where the TBC radiates as a near-blackbody. The operational wavelength minimizes interference from the high temperature and pressure environment. A hollow waveguide is used to transfer the radiation from the engine cavity to a high-speed detector and data acquisition system. A prototype of this system was successfully tested at an atmospheric burner test facility, and an on-engine version is undergoing testing for installation on a high-pressure rig.

  20. TREFEX: trend estimation and change detection in the response of MOX gas sensors.

    PubMed

    Pashami, Sepideh; Lilienthal, Achim J; Schaffernicht, Erik; Trincavelli, Marco

    2013-06-04

    Many applications of metal oxide gas sensors can benefit from reliable algorithms to detect significant changes in the sensor response. Significant changes indicate a change in the emission modality of a distant gas source and occur due to a sudden change of concentration or exposure to a different compound. As a consequence of turbulent gas transport and the relatively slow response and recovery times of metal oxide sensors, their response in open sampling configuration exhibits strong fluctuations that interfere with the changes of interest. In this paper we introduce TREFEX, a novel change point detection algorithm, especially designed for metal oxide gas sensors in an open sampling system. TREFEX models the response of MOX sensors as a piecewise exponential signal and considers the junctions between consecutive exponentials as change points. We formulate non-linear trend filtering and change point detection as a parameter-free convex optimization problem for single sensors and sensor arrays. We evaluate the performance of the TREFEX algorithm experimentally for different metal oxide sensors and several gas emission profiles. A comparison with the previously proposed GLR method shows a clearly superior performance of the TREFEX algorithm both in detection performance and in estimating the change time.

  1. PALLADIUM DOPED TIN OXIDE BASED HYDROGEN GAS SENSORS FOR SAFETY APPLICATIONS

    SciTech Connect

    Kasthurirengan, S.; Behera, Upendra; Nadig, D. S.

    2010-04-09

    Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd) are preferred due to their compactness and fast response. They detect hydrogen by monitoring the changes to the electrical, mechanical or optical properties of the films. We report the development of Pd-doped tin-oxide based gas sensors prepared on thin ceramic substrates with screen printed platinum (Pt) contacts and integrated nicrome wire heaters. The sensors are tested for their performances using hydrogen-nitrogen gas mixtures to a maximum of 4%H{sub 2} in N{sub 2}. The sensors detect hydrogen and their response times are less than a few seconds. Also, the sensor performance is not altered by the presence of helium in the test gas mixtures. By the above desired performance characteristics, field trials of these sensors have been undertaken. The paper presents the details of the sensor fabrication, electronic circuits, experimental setup for evaluation and the test results.

  2. Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High-T and Dynamic Gas Pressure in Harsh Environments

    SciTech Connect

    Xiao, Hai; Tsai, Hai-Lung; Dong, Junhang

    2014-09-30

    This is the final report for the program “Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High Temperature and Dynamic Gas Pressure in Harsh Environments”, funded by NETL, and performed by Missouri University of Science and Technology, Clemson University and University of Cincinnati from October 1, 2009 to September 30, 2014. Securing a sustainable energy economy by developing affordable and clean energy from coal and other fossil fuels is a central element to the mission of The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). To further this mission, NETL funds research and development of novel sensor technologies that can function under the extreme operating conditions often found in advanced power systems. The main objective of this research program is to conduct fundamental and applied research that will lead to successful development and demonstration of robust, multiplexed, microstructured silica and single-crystal sapphire fiber sensors to be deployed into the hot zones of advanced power and fuel systems for simultaneous measurements of high temperature and gas pressure. The specific objectives of this research program include: 1) Design, fabrication and demonstration of multiplexed, robust silica and sapphire fiber temperature and dynamic gas pressure sensors that can survive and maintain fully operational in high-temperature harsh environments. 2) Development and demonstration of a novel method to demodulate the multiplexed interferograms for simultaneous measurements of temperature and gas pressure in harsh environments. 3) Development and demonstration of novel sapphire fiber cladding and low numerical aperture (NA) excitation techniques to assure high signal integrity and sensor robustness.

  3. Sensor Nanny, data management services for marine observation operators

    NASA Astrophysics Data System (ADS)

    Loubrieu, Thomas; Détoc, Jérôme; Thorel, Arnaud; Azelmat, Hamza

    2016-04-01

    In marine sciences, the diversity of observed properties (from water physic to contaminants in observed in biological individuals or sediment) and observation methodologies (from manned sampling and analysis in labs to large automated networks of homogeneous platforms) requires different expertises and thus dedicated scientific program (ARGO, EMSO, GLOSS, GOSHIP, OceanSites, GOSUD, Geotrace, SOCAT, member state environment monitoring networks, experimental research…). However, all of them requires similar IT services to support the maintenance of their network (calibrations, deployment strategy, spare part management...) and their data management. In Europe, the National Oceanographic Data Centres coordinated by the IOC/IODE and SeaDataNet provide reliable reference services (e.g. vocabularies, contact directories), standards and long term data preservation. Besides the regional operational oceanographic centres (ROOSes) coordinated by EuroGOOS and Copernicus In-Situ Thematic Assembly Centre provide efficient data management for near real time or delayed mode services focused on physics and bio-geo-chemistry in the water column. Other e-infrastructures, such as euroBIS for biodiversity, are focused on specific disciplines. Beyond the current scope of these well established infrastructures, Sensor Nanny is a web application providing services for operators of observatories to manage their observations on the "cloud". The application stands against the reference services (vocabularies, organization directory) and standard profiles (OGC/Sensor Web Enablement) provided by SeaDataNet. The application provides an on-line editor to graphically describe, literally draw, their observatory (acquisition and processing systems). The observatory description is composed by the user from a palette of hundreds of pre-defined sensors or hardware linked together. In addition, the data providers can upload their data in CSV and netCDF formats on a dropbox-like system. The latest

  4. Advanced Gas Sensors Using SERS-Activated Waveguides

    NASA Astrophysics Data System (ADS)

    Lascola, Robert; McWhorter, Scott; Murph, Simona Hunyadi

    2010-08-01

    non-specific interactions between the surface coating and additional nanoparticles suspended in solution to which the analyte had been coupled. Clearly, for a gas sensor, such a scheme is not feasible, and in any event the reliance on the random configuration of the nanoparticles and the analyte is not expected to lead to efficient enhancement. Here, we report the creation of capillary coatings of self-assembled, aggregated high aspect ratio metallic nanoparticles (e.g. rod, wires) with a solution-phase technique. Self-assembly offers the possibility for a high density of SERS hot spots, which are often observed at the junction of adjacent particles. Shaped nanoparticles also enhance self-assembled deposition, and allow further control of the optical properties of the coating through manipulation of the morphology. SERS enhancements for gases are reported relative to mirrored capillaries and free-space measurements.

  5. Sensor Selection for Aircraft Engine Performance Estimation and Gas Path Fault Diagnostics

    NASA Technical Reports Server (NTRS)

    Simon, Donald L.; Rinehart, Aidan W.

    2016-01-01

    This paper presents analytical techniques for aiding system designers in making aircraft engine health management sensor selection decisions. The presented techniques, which are based on linear estimation and probability theory, are tailored for gas turbine engine performance estimation and gas path fault diagnostics applications. They enable quantification of the performance estimation and diagnostic accuracy offered by different candidate sensor suites. For performance estimation, sensor selection metrics are presented for two types of estimators including a Kalman filter and a maximum a posteriori estimator. For each type of performance estimator, sensor selection is based on minimizing the theoretical sum of squared estimation errors in health parameters representing performance deterioration in the major rotating modules of the engine. For gas path fault diagnostics, the sensor selection metric is set up to maximize correct classification rate for a diagnostic strategy that performs fault classification by identifying the fault type that most closely matches the observed measurement signature in a weighted least squares sense. Results from the application of the sensor selection metrics to a linear engine model are presented and discussed. Given a baseline sensor suite and a candidate list of optional sensors, an exhaustive search is performed to determine the optimal sensor suites for performance estimation and fault diagnostics. For any given sensor suite, Monte Carlo simulation results are found to exhibit good agreement with theoretical predictions of estimation and diagnostic accuracies.

  6. Sensor Selection for Aircraft Engine Performance Estimation and Gas Path Fault Diagnostics

    NASA Technical Reports Server (NTRS)

    Simon, Donald L.

    2015-01-01

    This paper presents analytical techniques for aiding system designers in making aircraft engine health management sensor selection decisions. The presented techniques, which are based on linear estimation and probability theory, are tailored for gas turbine engine performance estimation and gas path fault diagnostics applications. They enable quantification of the performance estimation and diagnostic accuracy offered by different candidate sensor suites. For performance estimation, sensor selection metrics are presented for two types of estimators including a Kalman filter and a maximum a posteriori estimator. For each type of performance estimator, sensor selection is based on minimizing the theoretical sum of squared estimation errors in health parameters representing performance deterioration in the major rotating modules of the engine. For gas path fault diagnostics, the sensor selection metric is set up to maximize correct classification rate for a diagnostic strategy that performs fault classification by identifying the fault type that most closely matches the observed measurement signature in a weighted least squares sense. Results from the application of the sensor selection metrics to a linear engine model are presented and discussed. Given a baseline sensor suite and a candidate list of optional sensors, an exhaustive search is performed to determine the optimal sensor suites for performance estimation and fault diagnostics. For any given sensor suite, Monte Carlo simulation results are found to exhibit good agreement with theoretical predictions of estimation and diagnostic accuracies.

  7. Gas storage project development, operation, and analysis: Basis guidelines for gas storage project development, operation, and operations analysis

    SciTech Connect

    Nowaczewski, S.F.

    1995-09-01

    Reservoir selection matches location, capacity, and deliverability to market demand; gathering, processing, compression, land acquisition, and pipeline connection significantly impact economics. Geologic considerations include field-wide variations in permeability, porosity, pay thickness. Well deliverability, and the number of wells required to meet targeted field deliverability can be estimated from kh or {phi}h. Analogous reservoir types can be used to estimate kh, {phi}h ranges for particular fields. Capillary pressure data define pore size distribution and gas-water threshold pressure. Existing well location and log data are essential in mapping subtle stratigraphic relationships. Definitions of field type, trap type, and liquid phases are important to the economics of storage development and operations, since safe high pressure storage is of greater benefit. Well construction considerations include location, type (vertical/slant/horizontal), and completion type to maximize drainage and deliverability; casing sizing to eliminate frictional pressure loss; and casing cementing for long-term mechanical integrity. Deliverability prediction uses well/gathering system nodal pressure data. The importance of deliverability maintenance/enhancement is increasing as markets demand ever greater deliverability. By design, a field allows cycling of an expected volume; loss of potential decreases efficiently. Inventory verification relies on well pressure and fluid data, accurate metering, and estimation of losses or leaks and fuel use. Data quality, quantity and management affect results in all these major areas of storage operations.

  8. Gas adsorption on monolayer blue phosphorus: implications for environmental stability and gas sensors.

    PubMed

    Liu, Nanshu; Zhou, Si

    2017-04-28

    Monolayer blue phosphorus has recently been synthesized by molecular beam epitaxial growth on Au(111) substrate. It is intriguing to compare this new 2D phase of phosphorus with phosphorene as to both fundamental properties and application prospects. Here, first-principles calculations are carried out to explore the adsorption behaviors of environmental gas molecules on monolayer blue phosphorus, including O2, NO, SO2, NH3, H2O, NO2, CO2, H2S, CO, and N2, and address their effects on the electronic properties of the material. Our calculations show that O2 is prone to dissociate and tends to chemisorb on the blue phosphorus sheet, phenomena which has also been observed in phosphorene. The other gas molecules can stably physisorb on monolayer blue phosphorus, showing different interaction strengths with the monolayer. These molecules induce distinct modifications to the band gap, carrier effective mass, and work function, which also depends on the molecular coverage. The responses of the electronic properties are subject to the charge transfer as well as alignment of the frontier molecular orbital levels of the gaseous molecules and band edges of the parent sheet. These results suggest that monolayer blue phosphorus is a promising candidate for novel gas sensors.

  9. Apparatus to characterize gas sensor response under real-world conditions in the lab.

    PubMed

    Kneer, J; Eberhardt, A; Walden, P; Ortiz Pérez, A; Wöllenstein, J; Palzer, S

    2014-05-01

    The use of semiconducting metal-oxide (MOX) based gas sensors in demanding applications such as climate and environmental research as well as industrial applications is currently hindered by their poor reproducibility, selectivity, and sensitivity. This is mainly due to the sensing mechanism which relies on the change of conductivity of the metal-oxide layer. To be of use for advanced applications metal-oxide (MOX) gas sensors need to be carefully prepared and characterized in laboratory environments prior to deployment. This paper describes the working principle, design, and use of a new apparatus that can emulate real-world conditions in the laboratory and characterize the MOX gas sensor signal in tailor-made atmospheres. In particular, this includes the control of trace gas concentrations and the control of oxygen and humidity levels which are important for the surface chemistry of metal-oxide based sensors. Furthermore, the sensor temperature can be precisely controlled, which is a key parameter of semiconducting, sensitive layers, and their response to particular gas compositions. The setup also allows to determine the power consumption of each device individually which may be used for performance benchmarking or monitoring changes of the temperature of the gas composition. Both, the working principle and the capabilities of the gas measurement chamber are presented in this paper employing tin dioxide (SnO2) based micro sensors as exemplary devices.

  10. Apparatus to characterize gas sensor response under real-world conditions in the lab

    NASA Astrophysics Data System (ADS)

    Kneer, J.; Eberhardt, A.; Walden, P.; Ortiz Pérez, A.; Wöllenstein, J.; Palzer, S.

    2014-05-01

    The use of semiconducting metal-oxide (MOX) based gas sensors in demanding applications such as climate and environmental research as well as industrial applications is currently hindered by their poor reproducibility, selectivity, and sensitivity. This is mainly due to the sensing mechanism which relies on the change of conductivity of the metal-oxide layer. To be of use for advanced applications metal-oxide (MOX) gas sensors need to be carefully prepared and characterized in laboratory environments prior to deployment. This paper describes the working principle, design, and use of a new apparatus that can emulate real-world conditions in the laboratory and characterize the MOX gas sensor signal in tailor-made atmospheres. In particular, this includes the control of trace gas concentrations and the control of oxygen and humidity levels which are important for the surface chemistry of metal-oxide based sensors. Furthermore, the sensor temperature can be precisely controlled, which is a key parameter of semiconducting, sensitive layers, and their response to particular gas compositions. The setup also allows to determine the power consumption of each device individually which may be used for performance benchmarking or monitoring changes of the temperature of the gas composition. Both, the working principle and the capabilities of the gas measurement chamber are presented in this paper employing tin dioxide (SnO2) based micro sensors as exemplary devices.

  11. Gas Hydrate Research Coring and Downhole Logging Operational Protocol

    NASA Astrophysics Data System (ADS)

    Collett, T. S.; Riedel, M.; Malone, M.

    2006-12-01

    Recent gas hydrate deep coring and downhole logging projects, including ODP Leg 204, IODP Expedition 311, and the India NGHP-01 effort have contributed greatly to our understanding of the geologic controls on the occurrence of gas hydrate. These projects have also built on the relatively sparse history of gas hydrate drilling experience to collectively develop a unique operational protocol to examine and sample gas hydrate in nature. The ideal gas hydrate research drill site in recent history, consists of at least three drill holes, with the first hole dedicated to LWD/MWD downhole logging in order to identify intervals to be pressurized cored and to collect critical petrophysical data. The second hole is usually dedicated for continuous coring operations. The third hole is used for special downhole tool measurements such as pressure coring and wire line logging. There is a strong scientific need to obtain LWD/MWD data prior to coring. The coring operations are complemented by frequent deployment of the PCS/HYACINTH pressure core systems. It is essential to know what the gas hydrate concentrations and vertical distribution are before deploying the available pressure core systems in order to choose the optimum depths for pressure coring operations. The coring operations are also complemented by frequent sampling for interstitial water, headspace gas, and microbiological analyses. Although those samples will be taken at relatively regular depths, the sampling frequency can be adjusted if gas hydrate concentrations and distribution can be forward predicted through the analysis of the LWD/MWD pre-core logging surveys. After completing the LWD/MWD logging program, usually as a dedicated drilling leg, field efforts will switch to conventional and pressure-controlled coring operations at each of the sites drilled during the LWD/MWD campaign. The standard continuous core hole will usually include APC coring to an expected refusal depth of ~100 mbsf; each hole is usually

  12. A Guidance Document for Kentucky's Oil and Gas Operations

    SciTech Connect

    None, None

    1998-11-10

    This technical report is a summary of the progress made for "A Guidance Document for Kentucky's Oil and Gas Operators". During this quarter, the document received continued review and editing in an elec-tronic format to satisfy the United States Department of Energy (DOE). Comments received from oil and gas operators reviewing this document prompted contact to be made with the United States Environmental Protection Agency (USEPA) to develop an addendum section to provide better explanation of USEPA requirements for Class II injection wells in Kentucky.

  13. Printable polythiophene gas sensor array for low-cost electronic noses

    NASA Astrophysics Data System (ADS)

    Chang, Josephine B.; Liu, Vincent; Subramanian, Vivek; Sivula, Kevin; Luscombe, Christine; Murphy, Amanda; Liu, Jinsong; Fréchet, Jean M. J.

    2006-07-01

    A route for generating arrays of printable polythiophene-based gas sensor materials suitable for low-cost manufacturing is demonstrated. Materials with complementary sensor responses are synthesized by incorporating functional groups into the molecule, either along the polymer backbone or as end-capping groups. Using these materials as printable sensor inks, a functional, integrated gas sensor array chip is fabricated using additive deposition techniques. The sensor array shows sensitivity to a range of volatile organic compounds down to concentrations of 10ppm. A three-terminal thin film transistor structure is used, allowing the extraction of multiple parameters that help to elucidate the mechanisms responsible for sensor response and the role of the functional groups in this response.

  14. Inflammable gas mixture detection with a single catalytic sensor based on the electric field effect.

    PubMed

    Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng

    2014-04-08

    This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%.

  15. Mixed-Potential Gas Sensors Using an Electrolyte Consisting of Zinc Phosphate Glass and Benzimidazole

    PubMed Central

    Akamatsu, Takafumi; Itoh, Toshio; Shin, Woosuck

    2017-01-01

    Mixed-potential gas sensors with a proton conductor consisting of zinc metaphosphate glass and benzimidazole were fabricated for the detection of hydrogen produced by intestinal bacteria in dry and humid air. The gas sensor consisting of an alumina substrate with platinum and gold electrodes showed good response to different hydrogen concentrations from 250 parts per million (ppm) to 25,000 ppm in dry and humid air at 100–130 °C. The sensor response varied linearly with the hydrogen and carbon monoxide concentrations due to mass transport limitations. The sensor responses to hydrogen gas (e.g., −0.613 mV to 1000 ppm H2) was higher than those to carbon monoxide gas (e.g., −0.128 mV to 1000 ppm CO) at 120 °C under atmosphere with the same level of humidity as expired air. PMID:28067788

  16. A single-nanoparticle NO2 gas sensor constructed using active molecular plasmonics.

    PubMed

    Chen, Lichan; Wu, Bo; Guo, Longhua; Tey, Ruiwen; Huang, Youju; Kim, Dong-Hwan

    2015-01-25

    A single-nanoparticle plasmonic sensor for the sensitive detection of gas molecules (NO2) has been constructed. Taking advantage of active molecular plasmonics, the analyte selectively triggers a measurable spectral shift of ferrocene-modified single gold nanorods.

  17. Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide.

    PubMed

    Hu, Nantao; Yang, Zhi; Wang, Yanyan; Zhang, Liling; Wang, Ying; Huang, Xiaolu; Wei, Hao; Wei, Liangmin; Zhang, Yafei

    2014-01-17

    Ultrafast and sensitive room temperature NH3 gas sensors based on chemically reduced graphene oxide (rGO) are demonstrated in this work. rGO, which was prepared via the reduction of graphene oxide by pyrrole, exhibited excellent responsive sensitivity and selectivity to ammonia (NH3) gas. The high sensing performance of these rGO sensors with resistance change as high as 2.4% and response time as fast as 1.4 s was realized when the concentration of NH3 gas was as low as 1 ppb. Furthermore, the rGO sensors could rapidly recover to their initial states with IR illumination. The devices also showed excellent repeatability and selectivity to NH3. These rGO sensors, with low cost, low power, and easy fabrication, as well as scalable properties, showed great potential for ultrasensitive detection of NH3 gas in a wide variety of fields.

  18. Growth of single wall carbon nanotubes using PECVD technique: An efficient chemiresistor gas sensor

    NASA Astrophysics Data System (ADS)

    Lone, Mohd Yaseen; Kumar, Avshish; Husain, Samina; Zulfequar, M.; Harsh; Husain, Mushahid

    2017-03-01

    In this work, the uniform and vertically aligned single wall carbon nanotubes (SWCNTs) have been grown on Iron (Fe) deposited Silicon (Si) substrate by plasma enhanced chemical vapor deposition (PECVD) technique at very low temperature of 550 °C. The as-grown samples of SWCNTS were characterized by field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM) and Raman spectrometer. SWCNT based chemiresistor gas sensing device was fabricated by making the proper gold contacts on the as-grown SWCNTs. The electrical conductance and sensor response of grown SWCNTs have been investigated. The fabricated SWCNT sensor was exposed to ammonia (NH3) gas at 200 ppm in a self assembled apparatus. The sensor response was measured at room temperature which was discussed in terms of adsorption of NH3 gas molecules on the surface of SWCNTs. The achieved results are used to develope a miniaturized gas sensor device for monitoring and control of environment pollutants.

  19. Exploitation of Unique Properties of Zeolites in the Development of Gas Sensors

    PubMed Central

    Zheng, Yangong; Li, Xiaogan; Dutta, Prabir K.

    2012-01-01

    The unique properties of microporous zeolites, including ion-exchange properties, adsorption, molecular sieving, catalysis, conductivity have been exploited in improving the performance of gas sensors. Zeolites have been employed as physical and chemical filters to improve the sensitivity and selectivity of gas sensors. In addition, direct interaction of gas molecules with the extraframework cations in the nanoconfined space of zeolites has been explored as a basis for developing new impedance-type gas/vapor sensors. In this review, we summarize how these properties of zeolites have been used to develop new sensing paradigms. There is a considerable breadth of transduction processes that have been used for zeolite incorporated sensors, including frequency measurements, optical and the entire gamut of electrochemical measurements. It is clear from the published literature that zeolites provide a route to enhance sensor performance, and it is expected that commercial manifestation of some of the approaches discussed here will take place. The future of zeolite-based sensors will continue to exploit its unique properties and use of other microporous frameworks, including metal organic frameworks. Zeolite composites with electronic materials, including metals will lead to new paradigms in sensing. Use of nano-sized zeolite crystals and zeolite membranes will enhance sensor properties and make possible new routes of miniaturized sensors. PMID:22666081

  20. The detection properties of ammonia SAW gas sensors based on L-glutamic acid hydrochloride.

    PubMed

    Shen, Chi-Yen; Huang, Chun-Pu; Huang, Wang-Tsung

    2005-10-01

    This study has investigated an improved surface acoustic wave (SAW) ammonia gas sensor based on L-glutamic acid hydrochloride. It presents an excellent reversibility, sensitivity, and repeatability to ammonia. The frequency shift versus ammonia concentration above 40 degrees C was a monotonic function, and the limit of detection of the sensor at 50 degrees C was 80 ppb.

  1. Operation and planning of coordinated natural gas and electricity infrastructures

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaping

    Natural gas is becoming rapidly the optimal choice for fueling new generating units in electric power system driven by abundant natural gas supplies and environmental regulations that are expected to cause coal-fired generation retirements. The growing reliance on natural gas as a dominant fuel for electricity generation throughout North America has brought the interaction between the natural gas and power grids into sharp focus. The primary concern and motivation of this research is to address the emerging interdependency issues faced by the electric power and natural gas industry. This thesis provides a comprehensive analysis of the interactions between the two systems regarding the short-term operation and long-term infrastructure planning. Natural gas and renewable energy appear complementary in many respects regarding fuel price and availability, environmental impact, resource distribution and dispatchability. In addition, demand response has also held the promise of making a significant contribution to enhance system operations by providing incentives to customers for a more flat load profile. We investigated the coordination between natural gas-fired generation and prevailing nontraditional resources including renewable energy, demand response so as to provide economical options for optimizing the short-term scheduling with the intense natural gas delivery constraints. As the amount and dispatch of gas-fired generation increases, the long-term interdependency issue is whether there is adequate pipeline capacity to provide sufficient gas to natural gas-fired generation during the entire planning horizon while it is widely used outside the power sector. This thesis developed a co-optimization planning model by incorporating the natural gas transportation system into the multi-year resource and transmission system planning problem. This consideration would provide a more comprehensive decision for the investment and accurate assessment for system adequacy and

  2. Development of Thermal Infrared Sensor to Supplement Operational Land Imager

    NASA Technical Reports Server (NTRS)

    Shu, Peter; Waczynski, Augustyn; Kan, Emily; Wen, Yiting; Rosenberry, Robert

    2012-01-01

    The thermal infrared sensor (TIRS) is a quantum well infrared photodetector (QWIP)-based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM). The TIRS instrument is a far-infrared imager operating in the pushbroom mode with two IR channels: 10.8 and 12 m. The focal plane will contain three 640 512 QWIP arrays mounted onto a silicon substrate. The readout integrated circuit (ROIC) addresses each pixel on the QWIP arrays and reads out the pixel value (signal). The ROIC is controlled by the focal plane electronics (FPE) by means of clock signals and bias voltage value. The means of how the FPE is designed to control and interact with the TIRS focal plane assembly (FPA) is the basis for this work. The technology developed under the FPE is for the TIRS focal plane assembly (FPA). The FPE must interact with the FPA to command and control the FPA, extract analog signals from the FPA, and then convert the analog signals to digital format and send them via a serial link (USB) to a computer. The FPE accomplishes the described functions by converting electrical power from generic power supplies to the required bias power that is needed by the FPA. The FPE also generates digital clocking signals and shifts the typical transistor-to-transistor logic (TTL) to }5 V required by the FPA. The FPE also uses an application- specific integrated circuit (ASIC) named System Image, Digitizing, Enhancing, Controlling, And Retrieving (SIDECAR) from Teledyne Corp. to generate the clocking patterns commanded by the user. The uniqueness of the FPE for TIRS lies in that the TIRS FPA has three QWIP detector arrays, and all three detector arrays must be in synchronization while in operation. This is to avoid data skewing while observing Earth flying in space. The observing scenario may be customized by uploading new control software to the SIDECAR.

  3. Ultrasensitive and Highly Selective Graphene-Based Single Yarn for Use in Wearable Gas Sensor

    PubMed Central

    Ju Yun, Yong; Hong, Won G.; Choi, Nak-Jin; Hoon Kim, Byung; Jun, Yongseok; Lee, Hyung-Kun

    2015-01-01

    Electric components based on fibers or textiles have been investigated owing to their potential applications in wearable devices. High performance on response to gas, drape-ability and washing durability are of important for gas sensors based on fiber substrates. In this report, we demonstrate the bendable and washable electronic textile (e-textile) gas sensors composed of reduced graphene oxides (RGOs) using commercially available yarn and molecular glue through an electrostatic self-assembly. The e-textile gas sensor possesses chemical durability to several detergent washing treatments and mechanical stability under 1,000 bending tests at an extreme bending radius of 1 mm as well as a high response to NO2 gas at room temperature with selectivity to other gases such as acetone, ethanol, ethylene, and CO2. PMID:26043109

  4. Ultrasensitive and Highly Selective Graphene-Based Single Yarn for Use in Wearable Gas Sensor

    NASA Astrophysics Data System (ADS)

    Ju Yun, Yong; Hong, Won G.; Choi, Nak-Jin; Hoon Kim, Byung; Jun, Yongseok; Lee, Hyung-Kun

    2015-06-01

    Electric components based on fibers or textiles have been investigated owing to their potential applications in wearable devices. High performance on response to gas, drape-ability and washing durability are of important for gas sensors based on fiber substrates. In this report, we demonstrate the bendable and washable electronic textile (e-textile) gas sensors composed of reduced graphene oxides (RGOs) using commercially available yarn and molecular glue through an electrostatic self-assembly. The e-textile gas sensor possesses chemical durability to several detergent washing treatments and mechanical stability under 1,000 bending tests at an extreme bending radius of 1 mm as well as a high response to NO2 gas at room temperature with selectivity to other gases such as acetone, ethanol, ethylene, and CO2.

  5. Ultrasensitive and highly selective graphene-based single yarn for use in wearable gas sensor.

    PubMed

    Yun, Yong Ju; Hong, Won G; Choi, Nak-Jin; Kim, Byung Hoon; Jun, Yongseok; Lee, Hyung-Kun

    2015-06-04

    Electric components based on fibers or textiles have been investigated owing to their potential applications in wearable devices. High performance on response to gas, drape-ability and washing durability are of important for gas sensors based on fiber substrates. In this report, we demonstrate the bendable and washable electronic textile (e-textile) gas sensors composed of reduced graphene oxides (RGOs) using commercially available yarn and molecular glue through an electrostatic self-assembly. The e-textile gas sensor possesses chemical durability to several detergent washing treatments and mechanical stability under 1,000 bending tests at an extreme bending radius of 1 mm as well as a high response to NO2 gas at room temperature with selectivity to other gases such as acetone, ethanol, ethylene, and CO2.

  6. Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures

    NASA Astrophysics Data System (ADS)

    Ohodnicki, Paul R.; Buric, Michael P.; Brown, Thomas D.; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

    2013-09-01

    Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by

  7. Occupation Competency Profile: Gas Utility Operator Certificate Program.

    ERIC Educational Resources Information Center

    Alberta Learning, Edmonton. Apprenticeship and Industry Training.

    This document presents information about the apprenticeship training program of Alberta, Canada, in general and the gas utility operator certificate program in particular. The first part of the document discusses the following items: Alberta's apprenticeship and industry training system; the occupation committee and its members; the Alberta…

  8. A micro-thermoelectric gas sensor for detection of hydrogen and atomic oxygen.

    PubMed

    Park, Se-Chul; Yoon, Seung-Il; Lee, Chung-il; Kim, Yong-Jun; Song, Soonho

    2009-02-01

    This paper demonstrates the fabrication and performance of a micro-thermoelectric gas sensor for an effective and inexpensive gas analysis system. The proposed micro-thermoelectric gas sensor was fabricated by using a surface micromachining technique. The sensing mechanism, consisting of thermoelectric material and a novel metal catalyst, was fabricated on the highly thermally resistive layer for reduced heat transfer to the substrate allowing for a simple fabrication process. The micro-thermoelectric gas sensor detects target gas species by measuring the reaction heat of the catalytic reaction between the target gas and a novel metal catalyst using Cu-Bi thermopiles. The catalytic reaction occurs only on the hot junction of the sensing thermopile where the metal catalyst is deposited. In order to reduce the external thermal noise, a difference between the output voltage of the sensing and the reference thermopiles was measured by using a differential amplifier. The response of the fabricated sensor was linear to temperature difference. The fabricated sensor can be used to detect various concentrations of hydrogen and atomic oxygen, where the output voltage linearly increased with the gas concentration.

  9. Global Environmental Micro Sensors Test Operations in the Natural Environment

    NASA Technical Reports Server (NTRS)

    Adams, Mark L.; Buza, Matthew; Manobianco, John; Merceret, Francis J.

    2007-01-01

    ENSCO, Inc. is developing an innovative atmospheric observing system known as Global Environmental Micro Sensors (GEMS). The GEMS concept features an integrated system of miniaturized in situ, airborne probes measuring temperature, relative humidity, pressure, and vector wind velocity. In order for the probes to remain airborne for long periods of time, their design is based on a helium-filled super-pressure balloon. The GEMS probes are neutrally buoyant and carried passively by the wind at predetermined levels. Each probe contains onboard satellite communication, power generation, processing, and geolocation capabilities. ENSCO has partnered with the National Aeronautics and Space Administration's Kennedy Space Center (KSC) for a project called GEMS Test Operations in the Natural Environment (GEMSTONE) that will culminate with limited prototype flights of the system in spring 2007. By leveraging current advances in micro and nanotechnology, the probe mass, size, cost, and complexity can be reduced substantially so that large numbers of probes could be deployed routinely to support ground, launch, and landing operations at KSC and other locations. A full-scale system will improve the data density for the local initialization of high-resolution numerical weather prediction systems by at least an order of magnitude and provide a significantly expanded in situ data base to evaluate launch commit criteria and flight rules. When applied to launch or landing sites, this capability will reduce both weather hazards and weather-related scrubs, thus enhancing both safety and cost-avoidance for vehicles processed by the Shuttle, Launch Services Program, and Constellation Directorates. The GEMSTONE project will conclude with a field experiment in which 10 to 15 probes are released over KSC in east central Florida. The probes will be neutrally buoyant at different altitudes from 500 to 3000 meters and will report their position, speed, heading, temperature, humidity, and

  10. Investigation of the Performance of HEMT-Based NO, NO₂ and NH₃ Exhaust Gas Sensors for Automotive Antipollution Systems.

    PubMed

    Halfaya, Yacine; Bishop, Chris; Soltani, Ali; Sundaram, Suresh; Aubry, Vincent; Voss, Paul L; Salvestrini, Jean-Paul; Ougazzaden, Abdallah

    2016-02-23

    We report improved sensitivity to NO, NO₂ and NH₃ gas with specially-designed AlGaN/GaN high electron mobility transistors (HEMT) that are suitable for operation in the harsh environment of diesel exhaust systems. The gate of the HEMT device is functionalized using a Pt catalyst for gas detection. We found that the performance of the sensors is enhanced at a temperature of 600 °C, and the measured sensitivity to 900 ppm-NO, 900 ppm-NO₂ and 15 ppm-NH₃ is 24%, 38.5% and 33%, respectively, at 600 °C. We also report dynamic response times as fast as 1 s for these three gases. Together, these results indicate that HEMT sensors could be used in a harsh environment with the ability to control an anti-pollution system in real time.

  11. Optoelectronic sensors for subsea oil and gas production

    NASA Astrophysics Data System (ADS)

    McStay, D.; Shiach, G.; Nolan, A.; McAvoy, S.

    2007-07-01

    The potential for optoelectronic sensor technology to provide the monitoring and control systems required for advanced subsea hydrocarbon production management is described. The utilisation of optoelectronic sensor technology to produce a new class of subsea Christmas Tree with in-built enhanced production monitoring and control systems as well as effective environmental monitoring systems is reported.

  12. Determination of chlorine concentration using single temperature modulated semiconductor gas sensor

    NASA Astrophysics Data System (ADS)

    Woźniak, Ł.; Kalinowski, P.; Jasiński, G.; Jasiński, P.

    2016-11-01

    A periodic temperature modulation using sinusoidal heater voltage was applied to a commercial SnO2 semiconductor gas sensor. Resulting resistance response of the sensor was analyzed using a feature extraction method based on Fast Fourier Transformation (FFT). The amplitudes of the higher harmonics of the FFT from the dynamic nonlinear responses of measured gas were further utilized as an input for Artificial Neuron Network (ANN). Determination of the concentration of chlorine was performed. Moreover, this work evaluates the sensor performance upon sinusoidal temperature modulation.

  13. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    SciTech Connect

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal

    2014-03-24

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  14. Development of Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Fralick, G.; Thomas, V.; Liu, C. C.; Wu, W. H.; Ward, B.; Makel, D.

    2002-01-01

    Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, fire detection, and environmental monitoring. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors. 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity. 3) The development of high temperature semiconductors, especially silicon carbide. However, due to issues of selectivity and cross-sensitivity, individual sensors are limited in the amount of information that they can provide in environments that contain multiple chemical species. Thus, sensor arrays are being developed to address detection needs in such multi-species environments. This paper discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, hydrazine, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

  15. Technical Survey and Evaluation of Underwater Sensors and Remotely Operated Vehicles

    DTIC Science & Technology

    1993-05-01

    and sensor technologies. "* An evaluation of how well each vehicle system would be able to meet operational and environmental requirements for sensor...delivery. "" An evaluation af how well each sensor would be able to meet the overall inspection requirements. "* The development of a conceptual...of damaged areas as well as crew efficiency and safety. 8 Precipitation (heavy snowfall, rain, or hail) contributes to low visibility, operator error

  16. Operating experience review of an INL gas monitoring system

    SciTech Connect

    Cadwallader, Lee C.; DeWall, K. G.; Herring, J. S.

    2015-03-12

    This article describes the operations of several types of gas monitors in use at the Idaho National Laboratory (INL) High Temperature Electrolysis Experiment (HTE) laboratory. The gases monitored in the lab room are hydrogen, carbon monoxide, carbon dioxide, and oxygen. The operating time, calibration, and both actual and unwanted alarms are described. The calibration session time durations are described. In addition, some simple calculations are given to estimate the reliability of these monitors and the results are compared to operating experiences of other types of monitors.

  17. Integrating event detection system operation characteristics into sensor placement optimization.

    SciTech Connect

    Hart, William Eugene; McKenna, Sean Andrew; Phillips, Cynthia Ann; Murray, Regan Elizabeth; Hart, David Blaine

    2010-05-01

    We consider the problem of placing sensors in a municipal water network when we can choose both the location of sensors and the sensitivity and specificity of the contamination warning system. Sensor stations in a municipal water distribution network continuously send sensor output information to a centralized computing facility, and event detection systems at the control center determine when to signal an anomaly worthy of response. Although most sensor placement research has assumed perfect anomaly detection, signal analysis software has parameters that control the tradeoff between false alarms and false negatives. We describe a nonlinear sensor placement formulation, which we heuristically optimize with a linear approximation that can be solved as a mixed-integer linear program. We report the results of initial experiments on a real network and discuss tradeoffs between early detection of contamination incidents, and control of false alarms.

  18. Optimal sensor locations for the backward Lagrangian stochastic technique in measuring lagoon gas emission

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluated the impact of gas concentration and wind sensor locations on the accuracy of the backward Lagrangian stochastic inverse-dispersion technique (bLS) for measuring gas emission rates from a typical lagoon environment. Path-integrated concentrations (PICs) and 3-dimensional (3D) wi...

  19. Forced assembly of water-dispersible carbon nanotubes trapped in paper for cheap gas sensors.

    PubMed

    Wang, Jian; Zhang, Xinyue; Huang, Xiaopeng; Wang, Shujun; Qian, Qiuping; Du, Wenbin; Wang, Yapei

    2013-11-25

    A versatile and readily scalable approach to fabricate a cheap and sensitive paper gas sensor is described. Chemically acidified single-walled carbon nanotubes are assembled in paper, forming continuous sensing arrays with a low detection limit and high detection selectivity for ammonia gas.

  20. Development of Fabric-Based Chemical Gas Sensors for Use as Wearable Electronic Noses

    PubMed Central

    Seesaard, Thara; Lorwongtragool, Panida; Kerdcharoen, Teerakiat

    2015-01-01

    Novel gas sensors embroidered into fabric substrates based on polymers/ SWNT-COOH nanocomposites were proposed in this paper, aiming for their use as a wearable electronic nose (e-nose). The fabric-based chemical gas sensors were fabricated by two main processes: drop coating and embroidery. Four potential polymers (PVC, cumene-PSMA, PSE and PVP)/functionalized-SWCNT sensing materials were deposited onto interdigitated electrodes previously prepared by embroidering conductive thread on a fabric substrate to make an optimal set of sensors. After preliminary trials of the obtained sensors, it was found that the sensors yielded a electrical resistance in the region of a few kilo-Ohms. The sensors were tested with various volatile compounds such as ammonium hydroxide, ethanol, pyridine, triethylamine, methanol and acetone, which are commonly found in the wastes released from the human body. These sensors were used to detect and discriminate between the body odors of different regions and exist in various forms such as the urine, armpit and exhaled breath odor. Based on a simple pattern recognition technique, we have shown that the proposed fabric-based chemical gas sensors can discriminate the human body odor from two persons. PMID:25602265

  1. Improving Drift Correction by Double Projection Preprocessing in Gas Sensor Arrays

    NASA Astrophysics Data System (ADS)

    Padilla, M.; Perera, A.; Montoliu, I.; Chaudry, A.; Persaud, K.; Marco, S.

    2009-05-01

    It is well known that gas chemical sensors are strongly affected by drift. Drift consist on changes in sensors responses along the time, which make that initial statistical models for gas or odor recognition become useless after a period of time of about weeks. Gas sensor arrays based instruments periodically need calibrations that are expensive and laborious. Many different statistical methods have been proposed to extend time between recalibrations. In this work, a simple preprocessing technique based on a double projection is proposed as a prior step to a posterior drift correction algorithm (in this particular case, Direct Orthogonal Signal Correction). This method highly improves the time stability of data in relation with the one obtained by using only such drift correction method. The performance of this technique will be evaluated on a dataset composed by measurements of three analytes by a polymer sensor array along ten months.

  2. Polymer coated quartz crystal microbalance sensors for detection of volatile organic compounds in gas mixtures.

    PubMed

    Si, Pengchao; Mortensen, John; Komolov, Alexei; Denborg, Jens; Møller, Preben Juul

    2007-08-06

    By coating different conducting polymers of thiophene and its derivatives on quartz crystal microbalance (QCM) sensor surfaces, new novel QCM gas sensors have been produced in two simple ways, which could classify testing gas samples of volatile organic compounds (VOCs) gases. Principle components analysis (PCA) has been performed based on the QCM measurement results, which shows that our QCM sensors array has very good utilizing potential on sensing both polar and low-polar/nonpolar VOC gases. The sensitivity, selectivity, reproducibility and detection limit of QCM sensors have also been discussed. Quantitative variation of sensitivity response with the increasing concentration has been studied. (PLS) analysis and prediction of concentrations of single gas in mixtures have been carried out.

  3. Chlorine sensing properties of zinc oxide resistive gas sensor doped with platinum

    NASA Astrophysics Data System (ADS)

    Fiedot, M.; Suchorska-Woźniak, P.; Rac, O.; Nawrot, W.; Teterycz, H.

    2016-11-01

    In presented studies resistive chlorine gas sensor with gas sensitive layer in the form of zinc oxide microrods doped with platinum was developed. The growth of active layer was carried out in water solution containing zinc nitrate (V), hexamethylenetetramine and chloroplatinic acid using the chemical bath deposition method. The structure and morphology of obtained sensors was characterized by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX). To determine the chlorine gas sensing properties Temperature-Stimulated Conductance method (TSC) was used. During the measurements sensor was tested in a reference atmosphere and an atmosphere with 2, 5 or 8 ppm of chlorine. Obtained results have shown that zinc oxide microrods doped with platinum were obtained. TSC measurements showed that developed sensor allows to detect chlorine with very good sensitivity.

  4. Development Of An Acoustice Sensor For On-Line Gas Temperature Measurement In Gasifiers

    SciTech Connect

    Peter Ariessohn; Hans Hornung

    2006-10-01

    This project was awarded under U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL) Program Solicitation DE-PS26-02NT41422 and specifically addresses Technical Topical Area 2 - Gasification Technologies. The project team includes Enertechnix, Inc. as the main contractor and ConocoPhillips Company as a technical partner, who also provides access to the SG Solutions Gasification Facility (formerly Wabash River Energy Limited), host for the field-testing portion of the research. The objective of this project was to adapt acoustic pyrometer technology to make it suitable for measuring gas temperature inside a coal gasifier, to develop a prototype sensor based on this technology, and to demonstrate its performance through testing on a commercial gasifier. The project was organized in three phases, each of approximately one year duration. The first phase consisted of researching a variety of sound generation and coupling approaches suitable for use with a high pressure process, evaluation of the impact of gas composition variability on the acoustic temperature measurement approach, evaluation of the impact of suspended particles and gas properties on sound attenuation, evaluation of slagging issues and development of concepts to deal with this issue, development and testing of key prototype components to allow selection of the best approaches, and development of a conceptual design for a field prototype sensor that could be tested on an operating gasifier. The second phase consisted of designing and fabricating a series of prototype sensors, testing them in the laboratory, and developing a conceptual design for a field prototype sensor. The third phase consisted of designing and fabricating the field prototype, and testing it in the lab and in a commercial gasifier to demonstrate the ability to obtain accurate measurements of gas temperature in an operating gasifier. This report describes all of the activities conducted during the project and

  5. Highly sensitive room temperature ammonia gas sensor based on Ir-doped Pt porous ceramic electrodes

    NASA Astrophysics Data System (ADS)

    Liu, Wenlong; Liu, Yen-Yu; Do, Jing-Shan; Li, Jing

    2016-12-01

    Room temperature NH3 gas sensors based on Pt and Pt-Ir (Ir doping Pt) porous ceramic electrodes have been fabricated by both electroplating and sputtering methods. The properties of the gaseous ammonia sensors have been examined by polarization and chronoamperometry techniques. The influence of humidity on the features of the resulting sensors in the system has also been discussed, and the working potential was optimized. Water vapors seem to hugely improve the electrochemical activity of the electrode. With increasing the relative humidity, the response of the Pt-Ir(E)/Pt(S)/PCP sensor to NH3 gas could be enhanced remarkably, and the sensitivity increases from 1.14 to 12.06 μA ppm-1 cm-2 .Then we have also discussed the sensing mechanism of the Pt-Ir sensor and the result has been confirmed by X-ray photoelectron spectroscopy of the electrode surface before and after reaction in the end.

  6. Investigation of thiol derivatized gold nanoparticle sensors for gas analysis

    NASA Astrophysics Data System (ADS)

    Stephens, Jared S.

    Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

  7. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    PubMed

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors.

  8. Silicon carbide-based hydrogen gas sensors for high-temperature applications.

    PubMed

    Kim, Seongjeen; Choi, Jehoon; Jung, Minsoo; Joo, Sungjae; Kim, Sangchoel

    2013-10-09

    We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures.

  9. Silicon Carbide-Based Hydrogen Gas Sensors for High-Temperature Applications

    PubMed Central

    Kim, Seongjeen; Choi, Jehoon; Jung, Minsoo; Joo, Sungjae; Kim, Sangchoel

    2013-01-01

    We investigated SiC-based hydrogen gas sensors with metal-insulator-semiconductor (MIS) structure for high temperature process monitoring and leak detection applications in fields such as the automotive, chemical and petroleum industries. In this work, a thin tantalum oxide (Ta2O5) layer was exploited with the purpose of sensitivity improvement, because tantalum oxide has good stability at high temperature with high permeability for hydrogen gas. Silicon carbide (SiC) was used as a substrate for high-temperature applications. We fabricated Pd/Ta2O5/SiC-based hydrogen gas sensors, and the dependence of their I-V characteristics and capacitance response properties on hydrogen concentrations were analyzed in the temperature range from room temperature to 500 °C. According to the results, our sensor shows promising performance for hydrogen gas detection at high temperatures. PMID:24113685

  10. Microfabricated Gas Sensors Demonstrated in Fire and Emission Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.

    2003-01-01

    A range of microfabricated chemical sensors are being developed to meet the needs of fire detection and emission monitoring in aerospace applications. These sensors have the advantages over traditional technology of minimal size, weight, and power consumption as well as the ability to be placed closer to where the measurements need to be made. Sensor arrays are being developed to address detection needs in environments where multiple species need to be measured. For example, the monitoring of chemical species such as carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons, and other species is important in the detection of fires on airplanes and spacecraft. In contrast, different sensors are necessary for characterizing some aircraft engine designs where the monitoring of nitrogen oxides (NO(x)) and CO is of high interest. Demonstration of both fire and emission microsensor technology was achieved this year in a collaborative effort undertaken by the NASA Glenn Research Center, Case Western Reserve University, and Makel Engineering, Inc.

  11. Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

    PubMed Central

    Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

    2009-01-01

    A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

  12. Design and fabrication of a CMOS-compatible MHP gas sensor

    SciTech Connect

    Li, Ying; Yu, Jun Wu, Hao; Tang, Zhenan

    2014-03-15

    A novel micro-hotplate (MHP) gas sensor is designed and fabricated with a standard CMOS technology followed by post-CMOS processes. The tungsten plugging between the first and the second metal layer in the CMOS processes is designed as zigzag resistor heaters embedded in the membrane. In the post-CMOS processes, the membrane is released by front-side bulk silicon etching, and excellent adiabatic performance of the sensor is obtained. Pt/Ti electrode films are prepared on the MHP before the coating of the SnO{sub 2} film, which are promising to present better contact stability compared with Al electrodes. Measurements show that at room temperature in atmosphere, the device has a low power consumption of ∼19 mW and a rapid thermal response of 8 ms for heating up to 300 °C. The tungsten heater exhibits good high temperature stability with a slight fluctuation (<0.3%) in the resistance at an operation temperature of 300 °C under constant heating mode for 336 h, and a satisfactory temperature coefficient of resistance of about 1.9‰/°C.

  13. Lightweight Fiber Optic Gas Sensor for Monitoring Regenerative Food Production

    NASA Technical Reports Server (NTRS)

    Schmidlin, Edward; Goswami, Kisholoy

    1995-01-01

    In this final report, Physical Optics Corporation (POC) describes its development of sensors for oxygen, carbon dioxide, and relative humidity. POC has constructed a phase fluorometer that can detect oxygen over the full concentration range from 0 percent to 100 percent. Phase-based measurements offer distinct advantages, such as immunity to source fluctuation, photobleaching, and leaching. All optics, optoelectronics, power supply, and the printed circuit board are included in a single box; the only external connections to the fluorometer are the optical fiber sensor and a power cord. The indicator-based carbon dioxide sensor is also suitable for short-term and discrete measurements over the concentration range from 0 percent to 100 percent. The optical fiber-based humidity sensor contains a porous core for direct interaction of the light beam with water vapor within fiber pores; the detection range for the humidity sensor is 10 percent to 100 percent, and response time is under five minutes. POC is currently pursuing the commercialization of these oxygen and carbon dioxide sensors for environmental applications.

  14. Gas Hydrate Research Site Selection and Operational Research Plans

    NASA Astrophysics Data System (ADS)

    Collett, T. S.; Boswell, R. M.

    2009-12-01

    In recent years it has become generally accepted that gas hydrates represent a potential important future energy resource, a significant drilling and production hazard, a potential contributor to global climate change, and a controlling factor in seafloor stability and landslides. Research drilling and coring programs carried out by the Ocean Drilling Program (ODP), the Integrated Ocean Drilling Program (IODP), government agencies, and several consortia have contributed greatly to our understanding of the geologic controls on the occurrence of gas hydrates in marine and permafrost environments. For the most part, each of these field projects were built on the lessons learned from the projects that have gone before them. One of the most important factors contributing to the success of some of the more notable gas hydrate field projects has been the close alignment of project goals with the processes used to select the drill sites and to develop the project’s operational research plans. For example, IODP Expedition 311 used a transect approach to successfully constrain the overall occurrence of gas hydrate within the range of geologic environments within a marine accretionary complex. Earlier gas hydrate research drilling, including IODP Leg 164, were designed primarily to assess the occurrence and nature of marine gas hydrate systems, and relied largely on the presence of anomalous seismic features, including bottom-simulating reflectors and “blanking zones”. While these projects were extremely successful, expeditions today are being increasingly mounted with the primary goal of prospecting for potential gas hydrate production targets, and site selection processes designed to specifically seek out anomalously high-concentrations of gas hydrate are needed. This approach was best demonstrated in a recently completed energy resource focused project, the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II (GOM JIP Leg II), which featured the collection of a

  15. Metal oxide nanowire gas sensors for indoor and outdoor environmental monitoring

    NASA Astrophysics Data System (ADS)

    Köck, Anton; Brunet, Elise; Freudenberg, Oliver; Gamauf, Christoph; Kraft, Jochen; Mutinati, Giorgio C.; Maier, Thomas; Nemecek, Alexander; Schrank, Franz; Schrems, Martin; Siegele, Martin; Siegert, Jörg; Steinhauer, Stephan; Teva, Jordi

    2013-05-01

    We present performance results of SnO2 and CuO nanowire gas sensor devices, where single and multi-nanowire device configurations have been employed in order to optimize sensor design. In particular the response to the target gases CO, H2, and H2S has been measured in dry and humid air; both the SnO2 and CuO nanowire sensors are able to detect CO in the low ppm concentration range, which is important for environmental monitoring. The CuO multi-nanowire devices show an extraordinary high response to H2S with sensitivity in the low ppb concentration. We present our developments of CMOS technology based micro-hotplates, which are employed as platform for gas sensitive thin films and nanowires. Potential heterogeneous integration of nanowires on the micro-hotplate chips as well as an approach towards gas sensor arrays is discussed. We conclude that CMOS integrated multi-nanowire gas sensors are highly promising candidates for the practical realization of multi-parameter sensor devices for indoor and outdoor environmental monitoring.

  16. Diode laser absorption sensors for gas-dynamic and combustion flows.

    PubMed

    Allen, M G

    1998-04-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  17. Diode laser absorption sensors for gas-dynamic and combustion flows

    NASA Technical Reports Server (NTRS)

    Allen, M. G.

    1998-01-01

    Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room

  18. Small CO2 Sensors Operate at Lower Temperature

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.

    2009-01-01

    Solid-electrolyte-based amperometric sensors for measuring concentrations of CO2 in air are being developed for use in detection of fires, environmental monitoring, and other applications where liquid-based electrochemical cells are problematic. These sensors are small (sizes of the order of a millimeter), are robust, are amenable to batch fabrication at relatively low cost, and exhibit short response times (seconds) and wide detection ranges. A sensor of this type at a previous stage of development included a solid electrolyte of Na3Zr2Si2PO12 deposited mainly between interdigitated Pt electrodes on an alumina substrate, all overcoated with an auxiliary solid electrolyte of (Na2CO3:BaCO3 in a molar ratio of 1:1.7). It was necessary to heat this device to a temperature as high as 600 C to obtain the desired sensitivity and rapid response. Heating sensors increases the power consumption of the sensor system and complicates the use of the sensor in some applications. Thus, decreasing a sensor s power consumption while maintaining its performance is a technical goal of ongoing development.

  19. Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures.

    PubMed

    Ohodnicki, Paul R; Buric, Michael P; Brown, Thomas D; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

    2013-10-07

    Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.

  20. Standard operating procedure: Gas atmosphere MELCO brazing furnace

    SciTech Connect

    Waller, C.R.

    1988-08-01

    A hydrogen and argon gas atmosphere furnace facility using electric furnaces is located at the Clinton P. Anderson Meson Physics Facility (LAMPF). This furnace system was acquired to handle smaller jobs with a more rapid response time than was possible with the larger furnaces. Accelerator- and experimental-related components best assembled by atmosphere brazing techniques are routinely processed by this facility in addition to special heat treatment and bakeout heats. The detailed operation sequence and description of the MELCO furnace system are covered by this report. This document is to augment LA-10231-SOP, which describes the operation of the large furnace systems. 6 figs.

  1. Interactive effect of hysteresis and surface chemistry on gated silicon nanowire gas sensors.

    PubMed

    Paska, Yair; Haick, Hossam

    2012-05-01

    Gated silicon nanowire gas sensors have emerged as promising devices for chemical and biological sensing applications. Nevertheless, the performance of these devices is usually accompanied by a "hysteresis" phenomenon that limits their performance under real-world conditions. In this paper, we use a series of systematically changed trichlorosilane-based organic monolayers to study the interactive effect of hysteresis and surface chemistry on gated silicon nanowire gas sensors. The results show that the density of the exposed or unpassivated Si-OH groups (trap states) on the silicon nanowire surface play by far a crucial effect on the hysteresis characteristics of the gated silicon nanowire sensors, relative to the effect of hydrophobicity or molecular density of the organic monolayer. Based on these findings, we provide a tentative model-based understanding of (i) the relation between the adsorbed organic molecules, the hysteresis, and the related fundamental parameters of gated silicon nanowire characteristics and of (ii) the relation between the hysteresis drift and possible screening effect on gated silicon nanowire gas sensors upon exposure to different analytes at real-world conditions. The findings reported in this paper could be considered as a launching pad for extending the use of the gated silicon nanowire gas sensors for discriminations between polar and nonpolar analytes in complex, real-world gas mixtures.

  2. Ammonia gas sensors based on poly (3-hexylthiophene)-molybdenum disulfide film transistors

    NASA Astrophysics Data System (ADS)

    Xie, Tao; Xie, Guangzhong; Su, Yuanjie; Hongfei, Du; Ye, Zongbiao; Jiang, Yadong

    2016-02-01

    In this work, in order to enhance the recovery performance of organic thin film transistors (OTFTs) ammonia (NH3) sensors, poly (3-hexylthiophene) (P3HT) and molybdenum disulfide (MoS2) were combined as sensitive materials. Different sensitive film structures as active layers of OTFTs, i.e., P3HT-MoS2 composite film, P3HT/MoS2 bilayer film and MoS2/P3HT bilayer film were fabricated by spray technology. OTFT gas sensors based on P3HT-MoS2 composite film showed a shorter recovery time than others when the ammonia concentration changed from 4 to 20 ppm. Specifically, x-ray diffraction (XRD), Raman and UV-visible absorption were employed to explore the interface properties between P3HT and single-layer MoS2. Through the complementary characterization, a mechanism based on charge transfer is proposed to explain the physical originality of these OTFT gas sensors: closer interlayer d-spacing and better π-π stacking of the P3HT chains in composite film have ensured a short recovery time of OTFT gas sensors. Moreover, sensing mechanisms of OTFTs were further studied by comparing the device performance in the presence of nitrogen or dry air as a carrier gas. This work not only strengthens the fundamental understanding of the sensing mechanism, but provides a promising approach to optimizing the OTFT gas sensors.

  3. Ammonia gas sensors based on poly (3-hexylthiophene)-molybdenum disulfide film transistors.

    PubMed

    Xie, Tao; Xie, Guangzhong; Su, Yuanjie; Hongfei, Du; Ye, Zongbiao; Jiang, Yadong

    2016-02-12

    In this work, in order to enhance the recovery performance of organic thin film transistors (OTFTs) ammonia (NH3) sensors, poly (3-hexylthiophene) (P3HT) and molybdenum disulfide (MoS2) were combined as sensitive materials. Different sensitive film structures as active layers of OTFTs, i.e., P3HT-MoS2 composite film, P3HT/MoS2 bilayer film and MoS2/P3HT bilayer film were fabricated by spray technology. OTFT gas sensors based on P3HT-MoS2 composite film showed a shorter recovery time than others when the ammonia concentration changed from 4 to 20 ppm. Specifically, x-ray diffraction (XRD), Raman and UV-visible absorption were employed to explore the interface properties between P3HT and single-layer MoS2. Through the complementary characterization, a mechanism based on charge transfer is proposed to explain the physical originality of these OTFT gas sensors: closer interlayer d-spacing and better π-π stacking of the P3HT chains in composite film have ensured a short recovery time of OTFT gas sensors. Moreover, sensing mechanisms of OTFTs were further studied by comparing the device performance in the presence of nitrogen or dry air as a carrier gas. This work not only strengthens the fundamental understanding of the sensing mechanism, but provides a promising approach to optimizing the OTFT gas sensors.

  4. A Guidance Document for Kentucky's Oil and Gas Operators

    SciTech Connect

    Kentucky Division of Oil and Gas

    1999-10-28

    This report is a summary of the accomplishments toward completion of ''A Guidance Document for Kentucky's Oil and Gas Operators.'' During this quarter, the document received continued review and editing in an electronic format to satisfy the United States Department of Energy (DOE). Comments received from oil and gas operators reviewing this document prompted contact to be made with the United States Environmental Protection Agency (USEPA) to develop an addendum section to provide better explanation of USEPA requirements for Class II injection wells in Kentucky. During February of this year the consultant hired to develop the Class II, UIC addendum section to the Guidance Document met with the USEPA and state personnel responsible for regulation of the Class II, UIC program in Kentucky. At this meeting a review of the federal and state regulatory procedures used for administration of the UIC program was made. Emphasis was directed to summarizing the addendum section in a format usable b y the small oil and gas operators in Kentucky. A draft of the addendum section is underway incorporating the ideas and comments received during this meeting. During the next quarter, a meeting of the subcommittee and Region IV of the USEPA will be scheduled. A review of a draft of the addendum section of the document will be made and necessary revisions incorporated toward final completion of the Guidance Document.

  5. Design and deployment of low-cost plastic optical fiber sensors for gas monitoring.

    PubMed

    Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

    2014-12-30

    This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva.

  6. Design and Deployment of Low-Cost Plastic Optical Fiber Sensors for Gas Monitoring

    PubMed Central

    Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

    2015-01-01

    This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva. PMID:25558990

  7. Gas sensor based on ZnO film/silica pillars

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Liang, Yaxiang; Yi, Futing; Wang, Bo; Zhang, Tianchong; Wang, Yuting; Zhou, Yue

    2016-12-01

    Silica submicron pillars are used as substrate for Zinc oxide (ZnO) gas sensor for the first time. The submicron pillars with the large surface ratio can improve the gas sensing performance obviously. Silicon pillars are fabricated by cesium chloride (CsCl) self-assembly lithography and inductively coupled plasma dry etching as substrate, the ZnO film is deposited on the pillars surface by RF magnetron sputtering. With this method, the pillar based gas sensor has the higher gas response, the shorter response and recovery time than the planar one with different working temperatures, different gas concentrations. 300 °C is the best working temperature, for planar gas sensor, the gas response is 22.81 for 1520 ppm ethanol, the response time is 55 s and the recovery time is 169 s. While for the pillar based one, the gas response is 28.20, the response time is 51 s and the recovery time is 92 s.

  8. Relevance of trapping mechanisms in certain Michigan formation stray sandstone gas reservoirs to gas storage operations

    SciTech Connect

    Nowaczewski, S.F. )

    1994-08-01

    The Stray sandstones of the Michigan Formation were early exploration targets in the Michigan basin. Subsequent to primary production, some of these reservoirs were converted to gas storage. Many of the Stray fields were discovered in an underpressured state, whereas peak storage pressures often exceed native brine gradients. It can be demonstrated that the Stray sandstones exist in sheets and lenses throughout the central basin area, and that gas/water contacts exist in the gas reservoirs but behave volumetrically. Various indirect and direct evidence indicates that gas is trapped structurally by the antiformal geometry of the sandstone bodies, by probable fracture-controlled porosity, stratigraphically by the isolation of parts of the sand bodies due to depositional and diagenetic influences, and by structurally controlled stratigraphic relationships. The understanding of the trapping mechanisms allows successful high pressure-gradient gas storage and leads to understanding reservoir behavior, which should result in efficient storage development and operation. Additional direct and secondary benefits of understanding Stray sandstone structure and stratigraphy are demonstrated for gas storage operation nuisances such as water production, and for use of the Stray as a window to or a type for deeper formations.

  9. Carbon Nanotube Sensors for Gas and Vapor Detection in Space and Terrestrial Applications

    NASA Technical Reports Server (NTRS)

    Li, Jing

    2005-01-01

    Viewgraphs detailing the development of a nanostructure engineered, portable, low cost, low power consumption, room temperature operated chemical sensor for space and terrestrial applications is presented. The topics include: 1) Applications and Requirements; 2) Nanotechnology Advantages; 3) Current Studies on NanoChemical Sensors; and 4) Our Research Status and Results.

  10. Gas pipeline leakage detection based on PZT sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Junxiao; Ren, Liang; Ho, Siu-Chun; Jia, Ziguang; Song, Gangbing

    2017-02-01

    In this paper, an innovative method for rapid detection and location determination of pipeline leakage utilizing lead zirconate titanate (PZT) sensors is proposed. The negative pressure wave (NPW) is a stress wave generated by leakage in the pipeline, and propagates along the pipeline from the leakage point to both ends. Thus the NPW is associated with hoop strain variation along the pipe wall. PZT sensors mounted on the pipeline were used to measure the strain variation and allowed accurate (within 2% error) and repeatable location (within 4% variance) of five manually controlled leakage points. Experimental results have verified the effectiveness and the location accuracy for leakage in a 55 meter long model pipeline.

  11. Method for Operating a Sensor to Differentiate Between Analytes in a Sample

    DOEpatents

    Kunt, Tekin; Cavicchi, Richard E; Semancik, Stephen; McAvoy, Thomas J

    1998-07-28

    Disclosed is a method for operating a sensor to differentiate between first and second analytes in a sample. The method comprises the steps of determining a input profile for the sensor which will enhance the difference in the output profiles of the sensor as between the first analyte and the second analyte; determining a first analyte output profile as observed when the input profile is applied to the sensor; determining a second analyte output profile as observed when the temperature profile is applied to the sensor; introducing the sensor to the sample while applying the temperature profile to the sensor, thereby obtaining a sample output profile; and evaluating the sample output profile as against the first and second analyte output profiles to thereby determine which of the analytes is present in the sample.

  12. Evaluation of infrared sensors for oil spill response operations. Final report, October 1994-June 1995

    SciTech Connect

    Hover, G.L.; Plourde, J.V.

    1995-06-01

    During November 1994, the USCO conducted a field evaluation of several commercially available portable infrared (IR) sensors for their ability to detect oil on water at night. The evaluation was conducted over the natural oil seeps off the coast of Santa Barbara, CA. The portable sensors were operated from the open door of a Coast Guard HH-60J helicopter. Sensors evaluated included the Agema Thermovision 1000 and Texas Instruments LOCUSP operating in the long wave IR (LWIR) and the Cincinnati Electronics IRC-160ST and IRRIS-256ST operating in the medium wave IR (MWIR). The installed FLIR 2000 LWIR system provided a baseline reference of current CG IR capabilities.

  13. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen

    PubMed Central

    Cardoza-Contreras, Marlene N.; Romo-Herrera, José M.; Ríos, Luis A.; García-Gutiérrez, R.; Zepeda, T. A.; Contreras, Oscar E.

    2015-01-01

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H2 pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H2. PMID:26690158

  14. Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen.

    PubMed

    Cardoza-Contreras, Marlene N; Romo-Herrera, José M; Ríos, Luis A; García-Gutiérrez, R; Zepeda, T A; Contreras, Oscar E

    2015-12-04

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H₂ pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H₂.

  15. Nanoparticle films made by gas phase synthesis: comparison of various techniques and sensor applications

    NASA Astrophysics Data System (ADS)

    Heszler, Peter; Reyes, L. F.; Hoel, Anders; Landstrom, Lars; Lantto, V.; Granqvist, Claes-Goran

    2003-07-01

    Nanoparticles can be generated by several different gas phase methods, such as gas deposition, laser-assisted chemical vapor deposition, and laser ablation. Some of the most important aspects - such as size-distribution, structure, and chemical composition of the generated nanoparticles (specifically W and WO3) - are presented and compared. WO3 nanoparticle films were deposited by an advanced gas deposition technique and were tested for sensor applications. Two different sensor devices were fabricated: Firstly, a thin Au-WO3 nanoparticle sandwich film was constructed, and conductance fluctuations of the Au film were measured as the sensor was exposed to alcohol vapor. Secondly, conductivity changes of a thick WO3 nanoparticle film were detected as it was exposed to test gases (H2S, NO2, and CO).

  16. Light-activated NO2 gas sensing of the networked CuO-decorated ZnS nanowire gas sensor

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Sun, Gun-Joo; Kheel, Hyejoon; Ko, Taegyung; Kim, Hyoun Woo; Lee, Chongmu

    2016-05-01

    CuO-decorated ZnS nanowires were synthesized by the thermal evaporation of ZnS powders followed by a solvothermal process for CuO decoration. The NO2 gas sensing properties of multiple-networked pristine and CuO-decorated ZnS nanowire sensors were then examined. The diameters of the CuO nanoparticles ranged from 20 to 60 nm. The multiple-networked pristine and CuO-decorated ZnS nanowire sensors showed the responses of 394 and 1055 %, respectively, to 5 ppm of NO2 at room temperature under UV illumination at 2.2 mW/cm2. The response and recovery times of the ZnS nanowire sensor to 5 ppm of NO2 were also reduced by decoration with the CuO nanoparticles. The responses of the sensors to NO2 at room temperature increased significantly with increasing UV illumination intensity. The underlying mechanisms for the enhanced response of the ZnS nanowire sensor to NO2 gas by CuO decoration and UV irradiation are discussed.

  17. Barriers Keep Drops Of Water Out Of Infrared Gas Sensors

    NASA Technical Reports Server (NTRS)

    Murray, Sean K.

    1996-01-01

    Infrared-sensor cells used for measuring partial pressures of CO(2) and other breathable gases modified to prevent entry of liquid water into sensory optical paths of cells. Hydrophobic membrane prevents drops of water entrained in flow from entering optical path from lamp to infrared detectors.

  18. Distinguishing between sensor fault, structural damage, and environmental or operational effects in structural health monitoring

    NASA Astrophysics Data System (ADS)

    Kullaa, Jyrki

    2011-11-01

    Discrimination between three different sources of variability in a vibration-based structural health monitoring system is investigated: environmental or operational effects, sensor faults, and structural damage. Separating the environmental or operational effects from the other two is based on the assumption that measurements under different environmental or operational conditions are included in the training data. Distinguishing between sensor fault and structural damage utilizes the fact that the sensor faults are local, while structural damage is global. By localizing the change to a sensor which is then removed from the network, the two different influences can be separated. The sensor network is modelled as a Gaussian process and the generalized likelihood ratio test (GLRT) is then used to detect and localize a change in the system. A numerical and an experimental study are performed to validate the proposed method.

  19. Experimental evaluation of stable long term operation of semiconductor magnetic sensors at ITER relevant environment

    NASA Astrophysics Data System (ADS)

    Bolshakova, I.; Belyaev, S.; Bulavin, M.; Brudnyi, V.; Chekanov, V.; Coccorese, V.; Duran, I.; Gerasimov, S.; Holyaka, R.; Kargin, N.; Konopleva, R.; Kost, Ya.; Kuech, T.; Kulikov, S.; Makido, O.; Moreau, Ph; Murari, A.; Quercia, A.; Shurygin, F.; Strikhanov, M.; Timoshyn, S.; Vasil'evskii, I.; Vinichenko, A.

    2015-08-01

    The paper deals with radiation resistant sensors and their associated measuring instrumentation developed in the course of R and D activities carried out in the framework of an international collaboration. The first trial tests of three-dimensional (3D) probes with Hall sensors have been performed in European tokamaks TORE SUPRA (2004) and JET (2005). Later in 2009 six sets of 3D probes were installed in JET and now continue to operate. The statistical analysis performed in 2014 on the basis of the JET database have demonstrated stable long term operation of all 18 sensors of 3D probes. The results of measurements conducted at the neutron fluxes of nuclear reactors have demonstrated the operability of the sensors up to high neutron fluences of F  >  1018n • cm-2 that exceeds the maximum one for the locations of steady state sensors in ITER over its total lifetime.

  20. Characterization and Modeling of Electrical Response of Electrode Catalyzed Reactions in AIGaN/GaN-Based Gas Sensors

    NASA Astrophysics Data System (ADS)

    Melby, Jacob H.

    AlGaN/GaN high electron mobility transistors (HEMT) and AlGaN/GaN diodes have promise for use as hydrogen and hydrocarbon sensors for a variety of industrial, military, and commercial applications. These semiconductor-based sensors have a number of advantages over other sensor technologies, such as the ability to operate at high temperatures, in corrosive environments, or under ionizing radiation. The high sensitivity of these devices to hydrogen-containing gases is associated with polarization differences within the AlGaN/GaN heterostructure that give rise to the formation of a two-dimensional electron gas (2DEG); exposure of the device to hydrogen changes the density of the 2DEG, which can be detected in a HEMT or diode structure. Although sensitivity to a range of gases has been reported, the factors that influence the behavior of the sensors are not well studied. The overarching goals of the research that follows were to determine how gas exposure conditions affect sensor behavior, to characterize and model the relationship between the electrical response of the sensors and the external gaseous environment, and to investigate the effects of using different metal catalysts on sensor behavior. The heterostructures used in this work were grown via metalorganic vapor phase epitaxy (MOVPE). Schottky diode and transistor devices employing platinum-group (Pd, Pt, Rh, Ir, Ru, and Os) catalysts were fabricated to allow electrical sensitivity in the presence of hydrogen and hydrogen containing gases. The generation of atomic hydrogen on the catalyst surface results in the rapid formation of hydrogen dipoles at the metal-semiconductor interface, which produces a measurable electronic response. The electrical response of Pt-gated HEMT-based sensors were measured in a flowing gaseous stream consisting of hydrogen in a pure nitrogen diluent at ambient and elevated temperatures. The transistors exhibited excellent transfer characteristics for temperatures ranging from 25

  1. Gas sensors based on one dimensional nanostructured metal-oxides: a review.

    PubMed

    Arafat, M M; Dinan, B; Akbar, Sheikh A; Haseeb, A S M A

    2012-01-01

    Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO(2), TiO(2), In(2)O(3), WO(x), AgVO(3), CdO, MoO(3), CuO, TeO(2) and Fe(2)O(3). Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

  2. Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review

    PubMed Central

    Arafat, M. M.; Dinan, B.; Akbar, Sheikh A.; Haseeb, A. S. M. A.

    2012-01-01

    Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research. PMID:22969344

  3. Residual gas analysis for long-pulse, advanced tokamak operation.

    PubMed

    Klepper, C C; Hillis, D L; Bucalossi, J; Douai, D; Oddon, P; Vartanian, S; Colas, L; Manenc, L; Pégourié, B

    2010-10-01

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This "diagnostic RGA" has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H(2)/D(2) isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H(2) injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H(2) could increase due to thermodesorption of overheated plasma facing components.

  4. Gas identification by dynamic measurements of SnO2 sensors

    NASA Astrophysics Data System (ADS)

    Vorobioff, Juan; Rodriguez, Daniel; Boselli, Alfredo; Lamagna, Alberto; Rinaldi, Carlos

    2011-09-01

    It is well know that the use of chambers with the sensors in the e-nose improves the measurements, due to a constant gas flow and the controlled temperature sensors[1]. Normally, the chamber temperature is above room temperature due to the heat generated by the heater of sensors. Also, the chamber takes a long time to reach a stable equilibrium temperature and it depends on enviromental conditions. Besides, the temperature variations modify the humidity producing variations in resistance measurements[2]. In this work using a heater system that controls the temperature of the chamber, the desorption process on SnO2 sensor array was study[3]. Also, it was fitted the data signal sensors using a two exponential decay functions in order to determine the desorbing constant process. These constants were used to classify and identify different alcohols and their concentrations.

  5. Gas sensors based on deposited single-walled carbon nanotube networks for DMMP detection

    NASA Astrophysics Data System (ADS)

    Wang, Yanyan; Zhou, Zhihua; Yang, Zhi; Chen, Xiaohang; Xu, Dong; Zhang, Yafei

    2009-08-01

    Sensors based on single-walled carbon nanotube (SWNT) networks were fabricated and their sensitive properties for the nerve agent stimulant dimethyl methylphosphonate (DMMP) vapor were investigated at room temperature. The SWNT networks were deposited on oxidized silicon surface functionalized with 3-aminopropyltrimethysilane (APS). Combining with a traditional silicon process, SWNT-based gas sensors were made at a wafer scale. The effects of the density of deposited SWNTs on the sensor response were studied. The excellent response is obtained under a density of 30-40 tubes µm-2. The sensors exhibit high resistance response, fast response time, rapid recovery and good reproducibility for DMMP vapor. The deposited SWNT sensors will be potentially extended to large-scale fabrication.

  6. Ad-Hoc Sensor Networks for Maritime Interdiction Operations and Regional Security

    DTIC Science & Technology

    2012-09-01

    which results in the coverage of every location of interest while other sensors of the network that do not possess vital data can hibernate to conserve...perform “sleep and wake up” and “ hibernation ” modes when there is no operational requirement. ARTEMIS has two platforms where sensors can be

  7. Effect of enhanced leachate recirculated (ELR) landfill operation and gas extraction on greenhouse gas emissions

    NASA Astrophysics Data System (ADS)

    Samir, Sonia

    The bioreactor/ enhanced leachate recirculated (ELR) landfill operation with the addition of moisture/ leachate to the landfill, accelerate the process of landfill waste decomposition; and increase the generation of LFG over a shorter period of time. Since emissions from the landfills are directly related to the gas generation, the increase in gas generation might also increase the emission from the landfill. On the contrary, the presence of gas extraction is suggested to mitigate the fugitive emissions from the landfills. Therefore, the motivation of the current study was to evaluate the effect of ELR operation as well as the gas extraction on the greenhouse gas emissions from the landfill. The current study was conducted in the City of Denton Landfill, Texas. Methane emission was investigated using a portable FID and static flux chamber technique from the landfill surface. Emission was measured from an ELR operated cell (cell 2) as well as a conventional cell (cell 0) in the City of Denton Landfill. Methane emission for cell 2 varied from 9544.3 ppm to 0 ppm while for cell 0, it varied from 0 ppm to 47 ppm. High spatial variations were observed during monitoring from both cells 0 and cell 2 which could be recognized as the variation of gas generation below the cover soil. The comparison between emissions from the slope and surface of the landfill showed that more methane emission occurred from the slopes than the top surface. In addition, the average landfill emission showed an increasing trend with increase in temperature and decreasing trend with increasing precipitation. The effect of ELR operation near the recirculation pipes showed a lag period between the recirculation and the maximum emission near the pipe. The emission near the pipe decreased after 1 day of recirculation and after the initial decrease, the emission started to increase and continued to increase up to 7 days after the recirculation. However, approximately after 10 days of recirculation, the

  8. Opportunities of Wireless Sensors and Controls for Building Operation

    SciTech Connect

    Kintner-Meyer, Michael CW; Conant, Rob

    2004-08-01

    This paper characterizes commercially available wireless technologies that are already being used in buildings applications or that are suitable for use in commercial buildings. The discussion provides an overview of fundamental concepts of radial broadcasting systems, as well as meshed networks, and will highlight the opportunities and challenges in their integration into existing wired control networks. This paper describes two demonstration projects of wireless sensors and their integration into existing control networks, and discusses their cost per sensor, their ease of installation, and their reliability. The authors will discuss the load control strategies implemented as a consequence of the wireless sensors and report on the energy and cost savings estimates. The paper will conclude with general future prospects for wireless technologies in buildings applications.

  9. 2D-MoO3 nanosheets for superior gas sensors

    NASA Astrophysics Data System (ADS)

    Ji, Fangxu; Ren, Xianpei; Zheng, Xiaoyao; Liu, Yucheng; Pang, Liuqing; Jiang, Jiaxing; Liu, Shengzhong (Frank)

    2016-04-01

    By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites.By taking advantages of both grinding and sonication, an effective exfoliation process is developed to prepare two-dimensional (2D) molybdenum oxide (MoO3) nanosheets. The approach avoids high-boiling-point solvents that would leave a residue and cause aggregation. Gas sensors fabricated using the 2D-MoO3 nanosheets provide a significantly enhanced chemical sensor performance. Compared with the sensors using bulk MoO3, the response of the 2D-MoO3 sensor increases from 7 to 33; the sensor response time is reduced from 27 to 21 seconds, and the recovery time is shortened from 26 to 10 seconds. We attribute the superior performance to the 2D-structure with a much increased surface area and reactive sites. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00880a

  10. EVALUATION OF SMOKE AND GAS SENSOR RESPONSES FOR FIRES OF COMMON MINE COMBUSTIBLES

    PubMed Central

    Perera, Inoka Eranda; Litton, Charles D.

    2015-01-01

    Experiments were conducted to evaluate the response characteristics of commercially available gas, smoke, and flame sensors to fires of common combustible mine materials. The experiments were conducted in the large-scale Fire gallery located at the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Laboratory (LLL) in Fairchance, PA, using Ponderosa Pine, Red Oak, Douglas-fir, high and low volatile coals, PVC and SBR conveyor belt, No. 2 diesel fuel, and diesel exhaust. All the experiments (except those using No. 2 diesel fuel and the diesel exhaust tests) were conducted in a similar manner, with combustible materials heated rapidly by electrical strip heaters producing smoldering fires that quickly transitioned into flaming fires. The sensors included a diffusion-type carbon monoxide (CO) sensor, photoelectric- and ionization-type smoke sensors, a video smoke/flame detector, and an optical flame detector. Simultaneous measurements were obtained for average gas concentrations, smoke mass concentrations, and smoke optical densities in order to quantify the levels of combustion products at the alert and alarm times of the sensors. Because the required sensor alarm levels are 10 ppm and 0.044 m−1 optical density for CO and smoke sensors, respectively, the different sensor alarms are compared to the time at which the CO and smoke reached these alarm levels (1). In addition, the potential impact of using smoke sensors that have met the performance standards from accredited testing laboratories is also evaluated using the response of an Underwriters’ Laboratory (UL)-approved combination photoelectric/ionization smoke detector. The results are discussed relative to fire sensor needs that can have a positive impact on mine fire safety. PMID:26229418

  11. High accuracy magnetic field sensors with wide operation temperature range

    NASA Astrophysics Data System (ADS)

    Vasil'evskii, I. S.; Vinichenko, A. N.; Rubakin, D. I.; Bolshakova, I. A.; Kargin, N. I.

    2016-10-01

    n+InAs(Si) epitaxial thin films heavily doped by silicon and Hall effect magnetic field sensors based on this structures have been fabricated and studied. We have demonstrated the successful formation of highly doped InAs thin films (∼100 nm) with the different intermediate layer arrangement and appropriate electron mobility values. Hall sensors performance parameters have been measured in wide temperature range. Obtained sensitivity varied from 1 to 40 Ω/T, while the best linearity and lower temperature coefficient have been found in the higher doped samples with lower electron mobility. We attribute this to the electron system degeneracy and decreased phonon contribution to electron mobility and resistance.

  12. Optical multi-species gas monitoring sensor and system

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor)

    2012-01-01

    The system includes at least one light source generating light energy having a corresponding wavelength. The system's sensor is based on an optical interferometer that receives light energy from each light source. The interferometer includes a free-space optical path disposed in an environment of interest. The system's sensor includes an optical device disposed in the optical path that causes light energy of a first selected wavelength to continue traversing the optical path whereas light energy of at least one second selected wavelength is directed away from the optical path. The interferometer generates an interference between the light energy of the first selected wavelength so-traversing the optical path with the light energy at the corresponding wavelength incident on the optical interferometer. A first optical detector detects the interference. At least one second detector detects the light energy at the at least one second selected wavelength directed away from the optical path.

  13. Surface acoustic wave gas sensor based on film conductivity changes

    NASA Astrophysics Data System (ADS)

    Ricco, A. J.; Martin, S. J.; Zipperian, T. E.

    1985-12-01

    The first surfce acoustic wave (SAW) sensor that functions via changes in conductivity of a thin surface film is reported. A lead phthalocyanine (PbPc) thin film is deposted on the acoustic progagation path of a LiNbO3 SAW delay line, which serves as the feedback element of an oscillator circuit. Reaction with strongly oxidizing gases, in particular NO2, increases the conductivity of the PbPc film. Acoustoelectric coupling of the traveling electric potential wave associated with the SAW-to-charge carriers in the PbPc film slows the acoustic wave velocity, altering the oscillation frequency of the circuit. This sensor is about 1000 times more sensitive, in terms of the number of NO2 molecules that can be detected (10 to the 16th molecules/cu cm of PbPc film), than an identical SAW sensor functioning via mass loading would be. Sensitivity to a few ppm of NO2 in N2 has been demonstrated.

  14. Surface acoustic wave gas sensor based on film conductivity changes

    NASA Astrophysics Data System (ADS)

    Ricco, A. J.; Martin, S. J.; Zipperian, T. E.

    The first surface acoustic wave (SAW) sensor that functions via changes in conductivity of a thin surface film is reported. A lead phthalocyanine (PbPc) thin film is deposited on the acoustic propagation path of a LiNbO3 SAW delay line, which serves as the feedback element of an oscillator circuit. Reaction with strongly oxidizing gases, in particular NO2, increases the conductivity of the PbPc film. Acoustoelectic coupling of the traveling electric potential wave associated with the SAW-to-charge carriers in the PbPc film slows the acoustic wave velocity, altering the oscillation frequency of the circuit. This sensor is about 1000 times more sensitive, in terms of the number of NO2 molecules that can be detected (10 to the 16th molecules/cu cm of PbPc film), than an identical SAW sensor functioning via mass loading would be. Sensitivity to a few ppm of NO2 in Ne was demonstrated.

  15. Morphology-Driven High-Performance Polymer Transistor-based Ammonia Gas Sensor.

    PubMed

    Yu, Seong Hoon; Cho, Jangwhan; Sim, Kyu Min; Ha, Jae Un; Chung, Dae Sung

    2016-03-01

    Developing high-performance gas sensors based on polymer field-effect transistors (PFETs) requires enhancing gas-capture abilities of polymer semiconductors without compromising their high charge carrier mobility. In this work, cohesive energies of polymer semiconductors were tuned by strategically inserting buffer layers, which resulted in dramatically different semiconductor surface morphologies. Elucidating morphological and structural properties of polymer semiconductor films in conjunction with FET studies revealed that surface morphologies containing large two-dimensional crystalline domains were optimal for achieving high surface areas and creating percolation pathways for charge carriers. Ammonia molecules with electron lone pairs adsorbed on the surface of conjugated semiconductors can serve as efficient trapping centers, which negatively shift transfer curves for p-type PFETs. Therefore, morphology optimization of polymer semiconductors enhances their gas sensing abilities toward ammonia, leading to a facile method of manufacturing high-performance gas sensors.

  16. Comparison of Orion Vision Navigation Sensor Performance from STS-134 and the Space Operations Simulation Center

    NASA Technical Reports Server (NTRS)

    Christian, John A.; Patangan, Mogi; Hinkel, Heather; Chevray, Keiko; Brazzel, Jack

    2012-01-01

    The Orion Multi-Purpose Crew Vehicle is a new spacecraft being designed by NASA and Lockheed Martin for future crewed exploration missions. The Vision Navigation Sensor is a Flash LIDAR that will be the primary relative navigation sensor for this vehicle. To obtain a better understanding of this sensor's performance, the Orion relative navigation team has performed both flight tests and ground tests. This paper summarizes and compares the performance results from the STS-134 flight test, called the Sensor Test for Orion RelNav Risk Mitigation (STORRM) Development Test Objective, and the ground tests at the Space Operations Simulation Center.

  17. Potential New Sensor for Use With Conventional Gas Carburizing

    NASA Technical Reports Server (NTRS)

    deGroot, W. A.

    1997-01-01

    Diagnostics developed for in-situ monitoring of rocket combustion environments have been adapted for use in heat treating furnaces. Simultaneous, in-situ monitoring of the carbon monoxide, carbon dioxide, methane, water, nitrogen and hydrogen concentrations in the endothermic gas of a heat treating furnace has been demonstrated under a Space Act Agreement between NASA Lewis, the Heat Treating Network, and Akron Steel Treating Company. Equipment installed at the Akron Steel Treating Company showed the feasibility of the method. Clear and well-defined spectra of carbon monoxide, nitrogen and hydrogen were obtained by means of an optical probe mounted on the endothermic gas line of a gas generator inside the plant, with the data reduction hardware located in the basement laboratory. Signals to and from the probe were transmitted via optical fibers.

  18. Response of electrochemical oxygen sensors to inert gas-air and carbon dioxide-air mixtures: measurements and mathematical modelling.

    PubMed

    Walsh, P T; Gant, S E; Dowker, K P; Batt, R

    2011-02-15

    Electrochemical oxygen gas sensors are widely used for monitoring the state of inertisation of flammable atmospheres and to warn of asphyxiation risks. It is well established but not widely known by users of such oxygen sensors that the response of the sensor is affected by the nature of the diluent gas responsible for the decrease in ambient oxygen concentration. The present work investigates the response of electrochemical sensors, with either acid or alkaline electrolytes, to gas mixtures comprising air with enhanced levels of nitrogen, carbon dioxide, argon or helium. The measurements indicate that both types of sensors over-read the oxygen concentrations when atmospheres contain high levels of helium. Sensors with alkaline electrolytes are also shown to underestimate the severity of the hazard in atmospheres containing high levels of carbon dioxide. This deviation is greater for alkaline electrolyte sensors compared to acid electrolyte sensors. A Computational Fluid Dynamics (CFD) model is developed to predict the response of an alkaline electrolyte, electrochemical gas sensor. Differences between predicted and measured sensor responses are less than 10% in relative terms for nearly all of the gas mixtures tested, and in many cases less than 5%. Extending the model to simulate responses of sensors with acid electrolytes would be straightforward.

  19. Using Bayesian Inference Framework towards Identifying Gas Species and Concentration from High Temperature Resistive Sensor Array Data

    DOE PAGES

    Liu, Yixin; Zhou, Kai; Lei, Yu

    2015-01-01

    High temperature gas sensors have been highly demanded for combustion process optimization and toxic emissions control, which usually suffer from poor selectivity. In order to solve this selectivity issue and identify unknown reducing gas species (CO, CH 4 , and CH 8 ) and concentrations, a high temperature resistive sensor array data set was built in this study based on 5 reported sensors. As each sensor showed specific responses towards different types of reducing gas with certain concentrations, based on which calibration curves were fitted, providing benchmark sensor array response database, then Bayesian inference framework was utilized to processmore » the sensor array data and build a sample selection program to simultaneously identify gas species and concentration, by formulating proper likelihood between input measured sensor array response pattern of an unknown gas and each sampled sensor array response pattern in benchmark database. This algorithm shows good robustness which can accurately identify gas species and predict gas concentration with a small error of less than 10% based on limited amount of experiment data. These features indicate that Bayesian probabilistic approach is a simple and efficient way to process sensor array data, which can significantly reduce the required computational overhead and training data.« less

  20. Integrated Analysis of Environment-driven Operational Effects in Sensor Networks

    SciTech Connect

    Park, Alfred J; Perumalla, Kalyan S

    2007-07-01

    There is a rapidly growing need to evaluate sensor network functionality and performance in the context of the larger environment of infrastructure and applications in which the sensor network is organically embedded. This need, which is motivated by complex applications related to national security operations, leads to a paradigm fundamentally different from that of traditional data networks. In the sensor networks of interest to us, the network dynamics depend strongly on sensor activity, which in turn is triggered by events in the environment. Because the behavior of sensor networks is sensitive to these driving phenomena, the integrity of the sensed observations, measurements and resource usage by the network can widely vary. It is therefore imperative to accurately capture the environmental phenomena, and drive the simulation of the sensor network operation by accounting fully for the environment effects. In this paper, we illustrate the strong, intimate coupling between the sensor network operation and the driving phenomena in their applications with an example sensor network designed to detect and track gaseous plumes.

  1. A sensor management architecture concept for monitoring emissions from open-air demil operations.

    SciTech Connect

    Johnson, Michael M.; Robinson, Jerry D.; Stoddard, Mary Clare; Horn, Brent A.; Lipkin, Joel; Foltz, Greg W.

    2005-09-01

    Sandia National Laboratories, CA proposed a sensor concept to detect emissions from open-burning/open-detonation (OB/OD) events. The system would serve two purposes: (1) Provide data to demilitarization operations about process efficiency, allowing process optimization for cleaner emissions and higher efficiency. (2) Provide data to regulators and neighboring communities about materials dispersing into the environment by OB/OD operations. The proposed sensor system uses instrument control hardware and data visualization software developed at Sandia National Laboratories to link together an array of sensors to monitor emissions from OB/OD events. The suite of sensors would consist of various physical and chemical detectors mounted on stationary or mobile platforms. The individual sensors would be wirelessly linked to one another and controlled through a central command center. Real-time data collection from the sensors, combined with integrated visualization of the data at the command center, would allow for feedback to the sensors to alter operational conditions to adjust for changing needs (i.e., moving plume position, increased spatial resolution, increased sensitivity). This report presents a systems study of the problem of implementing a sensor system for monitoring OB/OD emissions. The goal of this study was to gain a fuller understanding of the political, economic, and technical issues for developing and fielding this technology.

  2. Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source

    NASA Astrophysics Data System (ADS)

    Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

    2015-03-01

    An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

  3. Ammonia quantitative analysis model based on miniaturized Al ionization gas sensor and non-linear bistable dynamic model

    PubMed Central

    Ma, Rongfei

    2015-01-01

    In this paper, ammonia quantitative analysis based on miniaturized Al ionization gas sensor and non-linear bistable dynamic model was proposed. Al plate anodic gas-ionization sensor was used to obtain the current-voltage (I-V) data. Measurement data was processed by non-linear bistable dynamics model. Results showed that the proposed method quantitatively determined ammonia concentrations. PMID:25975362

  4. Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview.

    PubMed

    Woo, Hyung-Sik; Na, Chan Woong; Lee, Jong-Heun

    2016-09-20

    Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO₂, ZnO, and In₂O₃ are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C₂H₅OH and NO₂, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies-such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core-shell structures-have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

  5. Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

    PubMed Central

    Woo, Hyung-Sik; Na, Chan Woong; Lee, Jong-Heun

    2016-01-01

    Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors. PMID:27657076

  6. Optical sensor for carbon dioxide gas determination, characterization and improvements.

    PubMed

    Aguayo-López, M L; Capitán-Vallvey, L F; Fernández-Ramos, M D

    2014-08-01

    A study of different alternatives to improve the stability and lifetime of sensors for the determination of gaseous CO2 has been performed. It includes the characterization of different sensing membranes, a discussion of the results obtained and possibilities for the future. The solid sensor membrane for gaseous CO2 based on changes in the luminiscence of a luminophore immobilized on O2-insensitive film, concurrent with the displacement of a pH indicator, has some drawbacks, such as the loss of efficiency over time and the need to maintain the sensor in special atmospheric conditions. As a solution to these drawbacks, two alternatives were tested, the first alternative was replacing the newly proposed tetraoctyl ammonium hydroxide (TOAOH ) phase transfer agent with other basic agents that did not undergo a Hoffman degradation reaction, and the second alternative was the use of hydrophilic polymers that could retain water needed for CO2 sensing more efficiently. The different membranes tested indicated that the use of tetramethyl ammonium (TMAOH) instead of TOAOH as the phase transfer agent produced better results regarding stability and sensitivity. In addition, replacing the membrane polymer with hydrophilic polymers improved the sensing characteristics in terms of response time and stability over hydrophobic polymers. With a detection limit of 0.006%, the response time is 19s and the recovery time is 100s. The lifetime of the sensing membranes, which do not need to be held in any special atmosphere other than darkness, is longer than at least 300 days for membranes with TMAOH in hydrophilic polymer and 515 days for membranes with TMAOH in ethyl cellulose.

  7. Highly sensitive hydrogen sulfide (H2 S) gas sensors from viral-templated nanocrystalline gold nanowires

    NASA Astrophysics Data System (ADS)

    Moon, Chung Hee; Zhang, Miluo; Myung, Nosang V.; Haberer, Elaine D.

    2014-04-01

    A facile, site-specific viral-templated assembly method was used to fabricate sensitive hydrogen sulfide (H2S) gas sensors at room temperature. A gold-binding M13 bacteriophage served to organize gold nanoparticles into linear arrays which were used as seeds for subsequent nanowire formation through electroless deposition. Nanowire widths and densities within the sensors were modified by electroless deposition time and phage concentration, respectively, to tune device resistance. Chemiresistive H2S gas sensors with superior room temperature sensing performance were produced with sensitivity of 654%/ppmv, theoretical lowest detection limit of 2 ppbv, and 70% recovery within 9 min for 0.025 ppmv. The role of the viral template and associated gold-binding peptide was elucidated by removing organics using a short O2 plasma treatment followed by an ethanol dip. The template and gold-binding peptide were crucial to electrical and sensor performance. Without surface organics, the resistance fell by several orders of magnitude, the sensitivity dropped by more than a factor of 100 to 6%/ppmv, the lower limit of detection increased, and no recovery was detected with dry air flow. Viral templates provide a novel, alternative fabrication route for highly sensitive, nanostructured H2S gas sensors.

  8. Gas Sensors Based on Coated and Doped Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Li, Jing; Meyyappan, Meyya

    2008-01-01

    Efforts are underway to develop inexpensive, low-power electronic sensors, based on single-walled carbon nanotubes (SWCNTs), for measuring part-per-million and part-per-billion of selected gases (small molecules) at room temperature. Chemically unmodified SWCNTs are mostly unresponsive to typical gases that one might wish to detect. However, the electrical resistances of SWCNTs can be made to vary with concentrations of gases of interest by coating or doping the SWCNTs with suitable materials. Accordingly, the basic idea of the present development efforts is to incorporate thus-treated SWCNTs into electronic devices that measure their electrical resistances.

  9. Enhanced sensing properties of ZnO-SnO2 based composite type gas sensor

    NASA Astrophysics Data System (ADS)

    Mondal, Biplob; Das, Jayoti; Roychaudhuri, Chirosree; Mukharjee, Nillohit; Saha, Hiranmay

    2016-01-01

    Pure zinc oxide (ZnO) nanorods and zinc-tin oxide (ZnO-SnO2) composites based gas sensors were fabricated and tested for favorable gas sensing functionality. Systematic and comparative study on sensing properties like response magnitude, selectivity, response and recovery times, etc. of both the sensors were done for three test gases viz., hydrogen, methane and carbon mono-oxide. The obtained results clearly demonstrate enhanced sensing characteristics of the sensor made up of ZnO-SnO2 composites over that of pure ZnO nanorods based one. Fabricated sensors gave highest response and selectivity towards hydrogen at a relatively low temperature of 150 °C. The improved sensing properties of the sensor based on ZnO-SnO2 composites were attributed to the combined effect of the formation of depleted layer at the surface of individual ZnO/SnO2 microstructure as well as the formation of hetero-junction between ZnO and SnO2 grains. Sensing mechanism involved in the composite type ZnO-SnO2 based sensor has also been discussed.

  10. NDIR Gas Sensor for Spatial Monitoring of Carbon Dioxide Concentrations in Naturally Ventilated Livestock Buildings

    PubMed Central

    Mendes, Luciano B.; Ogink, Nico W. M.; Edouard, Nadège; van Dooren, Hendrik Jan C.; Tinôco, Ilda de Fátima F.; Mosquera, Julio

    2015-01-01

    The tracer gas ratio method, using CO2 as natural tracer, has been suggested as a pragmatic option to measure emissions from naturally ventilated (NV) barns without the need to directly estimate the ventilation rate. The aim of this research was to assess the performance of a low-cost Non-Dispersive Infra-Red (NDIR) sensor for intensive spatial field monitoring of CO2 concentrations in a NV dairy cow house. This was achieved by comparing NDIR sensors with two commonly applied methods, a Photo-Acoustic Spectroscope (PAS) Gas Monitor and an Open-Path laser (OP-laser). First, calibrations for the NDIR sensors were obtained in the laboratory. Then, the NDIR sensors were placed in a dairy cow barn for comparison with the PAS and OP-laser methods. The main conclusions were: (a) in order to represent the overall barn CO2 concentration of the dairy cow barn, the number of NDIR sensors to be accounted for average concentration calculation was dependent on barn length and on barn area occupation; and (b) the NDIR CO2 sensors are suitable for multi-point monitoring of CO2 concentrations in NV livestock barns, being a feasible alternative for the PAS and the OP-laser methods to monitor single-point or averaged spatial CO2 concentrations in livestock barns. PMID:25985166

  11. NDIR Gas Sensor for Spatial Monitoring of Carbon Dioxide Concentrations in Naturally Ventilated Livestock Buildings.

    PubMed

    Mendes, Luciano B; Ogink, Nico W M; Edouard, Nadège; van Dooren, Hendrik Jan C; Tinôco, Ilda de Fátima F; Mosquera, Julio

    2015-05-13

    The tracer gas ratio method, using CO2 as natural tracer, has been suggested as a pragmatic option to measure emissions from naturally ventilated (NV) barns without the need to directly estimate the ventilation rate. The aim of this research was to assess the performance of a low-cost Non-Dispersive Infra-Red (NDIR) sensor for intensive spatial field monitoring of CO2 concentrations in a NV dairy cow house. This was achieved by comparing NDIR sensors with two commonly applied methods, a Photo-Acoustic Spectroscope (PAS) Gas Monitor and an Open-Path laser (OP-laser). First, calibrations for the NDIR sensors were obtained in the laboratory. Then, the NDIR sensors were placed in a dairy cow barn for comparison with the PAS and OP-laser methods. The main conclusions were: (a) in order to represent the overall barn CO2 concentration of the dairy cow barn, the number of NDIR sensors to be accounted for average concentration calculation was dependent on barn length and on barn area occupation; and (b) the NDIR CO2 sensors are suitable for multi-point monitoring of CO2 concentrations in NV livestock barns, being a feasible alternative for the PAS and the OP-laser methods to monitor single-point or averaged spatial CO2 concentrations in livestock barns.

  12. Patterned electrode-based amperometric gas sensor for direct nitric oxide detection within microfluidic devices.

    PubMed

    Cha, Wansik; Tung, Yi-Chung; Meyerhoff, Mark E; Takayama, Shuichi

    2010-04-15

    This article describes a thin amperometric nitric oxide (NO) sensor that can be microchannel embedded to enable direct real-time detection of NO produced by cells cultured within the microdevice. A key for achieving the thin ( approximately 1 mm) planar sensor configuration required for sensor-channel integration is the use of gold/indium-tin oxide patterned electrode directly on a porous polymer membrane (pAu/ITO) as the base working electrode. The electrochemically deposited Au-hexacyanoferrate layer on pAu/ITO is used to catalyze NO oxidation to nitrite at lower applied potentials (0.65-0.75 V vs Ag/AgCl) and stabilize current output. Furthermore, use of a gas-permeable membrane to separate internal sensor compartments from the sample phase imparts excellent NO selectivity over common interfering agents (e.g., nitrite, ascorbate, ammonia, etc.) present in culture media and biological fluids. The optimized sensor design reversibly detects NO down to the approximately 1 nM level in stirred buffer and <10 nM in flowing buffer when integrated within a polymeric microfluidic device. We demonstrate utility of the channel-embedded sensor by monitoring NO generation from macrophages cultured within non-gas-permeable microchannels, as they are stimulated with endotoxin.

  13. Simulation and Fabrication of SAW-Based Gas Sensor with Modified Surface State of Active Layer and Electrode Orientation for Enhanced H2 Gas Sensing

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Nazibul; Maity, Santanu; Sarkar, Argha; Bhunia, Chandan Tilak; Acharjee, Debabrata; Joseph, Aneesh M.

    2017-02-01

    The design, analysis, optimization, and fabrication of layered and nanostructure-based surface acoustic wave (SAW) gas sensors are presented. A lithium niobate and zinc oxide (ZnO) nano multilayer structure is proposed to enhance the sensitivity of the SAW-based gas sensor. Different materials are considered for the intermediate layer in the design for optimization purposes. The sensitivity of the sensor could be improved due to increased active surface area obtained by varying the aspect ratio of the nanorods, the thickness of the intermediate layer, and the gap between the electrodes. The total displacement and frequency shift of the device were significantly improved. Overall, the mechanically engineered surface-based (nanorod) SAW gas sensor offered better sensing response than the layered SAW gas sensor in terms of sensitivity performance.

  14. Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.

    PubMed

    Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

    2013-12-15

    The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix.

  15. Application of Gas Sensor Arrays in Assessment of Wastewater Purification Effects

    PubMed Central

    Guz, Łukasz; Łagód, Grzegorz; Jaromin-Gleń, Katarzyna; Suchorab, Zbigniew; Sobczuk, Henryk; Bieganowski, Andrzej

    2015-01-01

    A gas sensor array consisting of eight metal oxide semiconductor (MOS) type gas sensors was evaluated for its ability for assessment of the selected wastewater parameters. Municipal wastewater was collected in a wastewater treatment plant (WWTP) in a primary sedimentation tank and was treated in a laboratory-scale sequential batch reactor (SBR). A comparison of the gas sensor array (electronic nose) response to the standard physical-chemical parameters of treated wastewater was performed. To analyze the measurement results, artificial neural networks were used. E-nose—gas sensors array and artificial neural networks proved to be a suitable method for the monitoring of treated wastewater quality. Neural networks used for data validation showed high correlation between the electronic nose readouts and: (I) chemical oxygen demand (COD) (r = 0.988); (II) total suspended solids (TSS) (r = 0.938); (III) turbidity (r = 0.940); (IV) pH (r = 0.554); (V) nitrogen compounds: N-NO3 (r = 0.958), N-NO2 (r = 0.869) and N-NH3 (r = 0.978); (VI) and volatile organic compounds (VOC) (r = 0.987). Good correlation of the abovementioned parameters are observed under stable treatment conditions in a laboratory batch reactor. PMID:25545263

  16. A Gas-Sensor-Based Urea Enzyme Electrode: Its Construction and Use in the Undergraduate Laboratory.

    ERIC Educational Resources Information Center

    Riechel, Thomas L.

    1984-01-01

    Describes an undergraduate experiment for the potentiometric determination of urea based on the physical entrapment of urease on the tip of an ammonia gas sensor. An advantage of this technique is the ease with which the ammonia electrode can be converted to a urea electrode. (JN)

  17. Operational characteristics of the dispersed sensor processor mesh. [for avionics

    NASA Technical Reports Server (NTRS)

    Abbott, L. W.

    1983-01-01

    The dispersed sensor processing mesh (DSPM) is part of an experimental system used to pursue a proof of concept for an advanced fault-tolerant communication strategy. The DSPM experiments incorporate sensors and effectors into an ultra-reliable nodal network in which a central bus controller performs algorithms to grow and maintain the network. The experiments demonstrate that DSPM is an achievable communication network that can sustain failures and continue to function properly. The results of the experiment give insights into the unique characteristics of the DSPM network and the network's capacity to limit physical damage propagation, limit damaged-data propagation, and to survive cyclic communication paths. This paper describes the concept, mechanization, and performance of the DSPM system in a real-time flight-critical environment.

  18. Phase Noise Squeezing Based Parametric Bifurcation Tracking of MIP-Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing

    DTIC Science & Technology

    2014-06-08

    can be calculated based on the flow rate and oven temperature for a specific permeation tube. The sensor response is detected by an optical laser...Based Parametric Bifurcation Tracking of Mip-Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing See Attached The views, opinions and/or...2050 1 ABSTRACT Phase Noise-Squeezing-Based Parametric Bifurcation Tracking of Mip-Coated Microbeam MEMS Sensor for TNT Explosive Gas Sensing

  19. Automatic Carbon Dioxide-Methane Gas Sensor Based on the Solubility of Gases in Water

    PubMed Central

    Cadena-Pereda, Raúl O.; Rivera-Muñoz, Eric M.; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J.; Anaya-Rivera, Ely K.

    2012-01-01

    Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0–100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible. PMID:23112626

  20. Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

    PubMed Central

    Some, Surajit; Xu, Yang; Kim, Youngmin; Yoon, Yeoheung; Qin, Hongyi; Kulkarni, Atul; Kim, Taesung; Lee, Hyoyoung

    2013-01-01

    New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor. PMID:23736838

  1. Automatic carbon dioxide-methane gas sensor based on the solubility of gases in water.

    PubMed

    Cadena-Pereda, Raúl O; Rivera-Muñoz, Eric M; Herrera-Ruiz, Gilberto; Gomez-Melendez, Domingo J; Anaya-Rivera, Ely K

    2012-01-01

    Biogas methane content is a relevant variable in anaerobic digestion processing where knowledge of process kinetics or an early indicator of digester failure is needed. The contribution of this work is the development of a novel, simple and low cost automatic carbon dioxide-methane gas sensor based on the solubility of gases in water as the precursor of a sensor for biogas quality monitoring. The device described in this work was used for determining the composition of binary mixtures, such as carbon dioxide-methane, in the range of 0-100%. The design and implementation of a digital signal processor and control system into a low-cost Field Programmable Gate Array (FPGA) platform has permitted the successful application of data acquisition, data distribution and digital data processing, making the construction of a standalone carbon dioxide-methane gas sensor possible.

  2. Gas Sensors Based on Single-Arm Waveguide Interferometers

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey; Curley, Michael; Diggs, Darnell; Adamovsky, Grigory

    1998-01-01

    Various optical technologies can be implemented in chemical sensing. Sensitive, rugged, and compact systems will be more likely built using interferometric waveguide sensors. Currently existing sensors comprise dual-arm systems with external reference arm, dual-arm devices with internal reference arm such as integrated Mach-Zehnder interferometer, and single-arm systems which employ the interference between different waveguide modes. These latter ones are the most compact and rugged but still sensitive enough to monitor volatile pollutants such as NH3 coming out of industrial refrigerators and fertilizer plants and stocks, NO, NO2, SO2, emitted by industrial burning processes. Single-arm devices in planar waveguide configuration most frequently use two orthogonally polarized modes TE (sub i) and TM (sub i) of the same order i. Sensing effect is based on the difference in propagation conditions for the modes caused by the environment. However, dual-mode single-order interferometers still have relatively low sensitivity with respect to the environment related changes in the waveguide core because of small difference between propagation constants of TE (sub i) and TM (sub i) modes of the same order. Substantial sensitivity improvement without significant complication can be achieved for planar waveguide interferometers using modes of different orders with much greater difference between propagation constants.

  3. Sensor system for Greenhouse Gas Observing Satellite (GOSAT)

    NASA Astrophysics Data System (ADS)

    Hamazaki, Takashi; Kuze, Akihiko; Kondo, Kayoko

    2004-11-01

    Global warming has become a very serious issue for human beings. In 1997, the Kyoto Protocol was adopted at the Third Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP3), making it mandatory for developed nations to reduce carbon dioxide emissions by six (6) to eight (8) per cent of their total emissions in 1990, and to meet this goal sometime between 2008 and 2012. The Greenhouse gases Observing SATellite (GOSAT) is design to monitor the global distribution of carbon dioxide (CO2) from orbit. GOSAT is a joint project of Japan Aerospace Exploration Agency (JAXA), the Ministry of Environment (MOE), and the National Institute for Environmental Studies (NIES). JAXA is responsible for the satellite and instrument development, MOE is involved in the instrument development, and NIES is responsible for the satellite data retrieval. The satellite is scheduled to be launched in 2008. In order to detect the CO2 variation of boundary layers, both the technique to measure the column density and the retrieval algorithm to remove cloud and aerosol contamination are investigated. Main mission sensor of the GOSAT is a Fourier Transform Spectrometer with high optical throughput, spectral resolution and wide spectral coverage, and a cloud-aerosol detecting imager attached to the satellite. The paper presents the mission sensor system of the GOSAT together with the results of performance demonstration with proto-type instrument aboard an aircraft.

  4. A Guidance Document for Kentucky's Oil and Gas Operators

    SciTech Connect

    Bender Rick

    1999-10-28

    This technical report is a summary of the accomplishments toward completion of ''A Guidance Document for Kentucky's Oil and Gas Operators''. During this quarter, the document received continued review and editing in an electronic format to satisfy the United States Department of Energy (DOE). Comments received from oil and gas operators reviewing this document prompted contact to be made with the United States Environmental Protection Agency (U. S. EPA) to develop an addendum section to provide better explanation of U.S. EPA requirements for Class II injection wells in Kentucky. During May of this year the consultant hired to develop the Class II, UIC addendum section to the guidance document met a second time with the U.S. EPA and state personnel responsible for regulation of the Class II, UIC program in Kentucky, to review a draft of the document. This draft was discussed during the meeting with the U.S. EPA and will receive additional editing and comment during the next quarter.

  5. Simplified gas sensor model based on AlGaN/GaN heterostructure Schottky diode

    NASA Astrophysics Data System (ADS)

    Das, Subhashis; Majumdar, S.; Kumar, R.; Chakraborty, A.; Bag, A.; Biswas, D.

    2015-08-01

    Physics based modeling of AlGaN/GaN heterostructure Schottky diode gas sensor has been investigated for high sensitivity and linearity of the device. Here the surface and heterointerface properties are greatly exploited. The dependence of two dimensional electron gas (2DEG) upon the surface charges is mainly utilized. The simulation of Schottky diode has been done in Technology Computer Aided Design (TCAD) tool and I-V curves are generated, from the I-V curves 76% response has been recorded in presence of 500 ppm gas at a biasing voltage of 0.95 Volt.

  6. Simplified gas sensor model based on AlGaN/GaN heterostructure Schottky diode

    SciTech Connect

    Das, Subhashis Majumdar, S.; Kumar, R.; Bag, A.; Chakraborty, A.; Biswas, D.

    2015-08-28

    Physics based modeling of AlGaN/GaN heterostructure Schottky diode gas sensor has been investigated for high sensitivity and linearity of the device. Here the surface and heterointerface properties are greatly exploited. The dependence of two dimensional electron gas (2DEG) upon the surface charges is mainly utilized. The simulation of Schottky diode has been done in Technology Computer Aided Design (TCAD) tool and I-V curves are generated, from the I-V curves 76% response has been recorded in presence of 500 ppm gas at a biasing voltage of 0.95 Volt.

  7. Combined raman and IR fiber-based sensor for gas detection

    DOEpatents

    Carter, Jerry C; Chan, James W; Trebes, James E; Angel, Stanley M; Mizaikoff, Boris

    2014-06-24

    A double-pass fiber-optic based spectroscopic gas sensor delivers Raman excitation light and infrared light to a hollow structure, such as a hollow fiber waveguide, that contains a gas sample of interest. A retro-reflector is placed at the end of this hollow structure to send the light back through the waveguide where the light is detected at the same end as the light source. This double pass retro reflector design increases the interaction path length of the light and the gas sample, and also reduces the form factor of the hollow structure.

  8. Deodorant Characteristics of Breath Odor Occurred from Favorite Foods Using Metal Oxide Gas Sensors

    NASA Astrophysics Data System (ADS)

    Seto, Shuichi; Oyabu, Takashi; Cai, Kuiqian; Katsube, Teruaki

    Three types of metal oxide gas sensors were adopted to detect the degree of breath odor. Various sorts of information are included in the odor. Each sensor has different sensitivities to gaseous chemical substances and the sensitivities also differ according to human behaviors, for example taking a meal, teeth-brushing and drinking something. There is also a possibility that the sensor can detect degrees of daily fatigue. Sensor sensitivities were low for the expiration of the elderly when the subject drank green tea. In this study, it is thought that the odor system can be incorporated into a healing robot. The robot can communicate with the elderly using several words and also connect to Internet. As for the results, the robot can identify basic human behaviors and recognize the living conditions of the resident. Moreover, it can also execute a kind of information retrieval through the Internet. Therefore, it has healing capability for the aged, and can also receive and transmit information.

  9. Highly sensitive gas leak detector based on a quartz-enhanced photoacoustic SF6 sensor.

    PubMed

    Sampaolo, Angelo; Patimisco, Pietro; Giglio, Marilena; Chieco, Leonardo; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

    2016-07-11

    The implementation, performance validation, and testing of a gas-leak optical sensor based on mid-IR quartz-enhanced photoacoustic (QEPAS) spectroscopic technique is reported. A QEPAS sensor was integrated in a vacuum-sealed test station for mechatronic components. The laser source for the sensor is a quantum cascade laser emitting at 10.56 µm, resonant with a strong absorption band of sulfur hexafluoride (SF6), which was selected as a leak tracer. The minimum detectable concentration of the QEPAS sensor is 2.7 parts per billion with an integration time of 1 s, corresponding to a sensitivity of leak flows in the 10-9 mbar∙l/s range, comparable with state-of-the-art leak detection techniques.

  10. Development of MWCNTs/alumina composite-based sensor for trace level ammonia gas sensing

    NASA Astrophysics Data System (ADS)

    Sharma, Sakshi; Hussain, Shahir; Sengupta, K.; Islam, S. S.

    2013-06-01

    Multi-walled carbon nanotube (MWCNT)/alumina (Al2O3) composite thin film-based low cost, rigid and highly efficient sensors were developed for trace level ammonia (NH3) gas sensing applications. Composite films were prepared by dispersing MWCNTs in varying concentration in alumina solution following the sol-gel process. The sensor response as a function MWCNT concentrations were measured and compared. The notable characteristics of these sensors are fast response time (10 minutes), and excellent reproducibility with detection level up to 6 ppm. Although poor NH3 desorption causes a high recovery time, fast and complete recovery was acquired using appropriate thermal treatment protocol. The sensitivity was found to be proportional to NH3 concentrations in the range 6-25 ppm and then gradually saturated at higher concentrations. However, a decrease in the sensor response was observed with increase in concentrations of MWCNTs.

  11. Research and Development of Non-Spectroscopic MEMS-Based Sensor Arrays for Targeted Gas Detection

    SciTech Connect

    Loui, A; McCall, S K

    2011-10-24

    The ability to monitor the integrity of gas volumes is of interest to the stockpile surveillance community. Specifically, the leak detection of noble gases, at relevant concentration ranges and distinguished from other chemical species that may be simultaneously present, is particularly challenging. Aside from the laboratory-based method of gas chromatography-mass spectrometry (GC-MS), where samples may be collected by solid-phase microextraction (SPME) or cryofocusing, the other major approaches for gas-phase detection employ lasers typically operating in the mid-infrared wavelength region. While mass spectrometry can readily detect noble gases - the helium leak detector is an obvious example - laser-based methods such as infrared (IR) or Raman spectroscopy are completely insensitive to them as their monatomic nature precludes a non-zero dipole moment or changes in polarizability upon excitation. Therefore, noble gases can only be detected by one of two methods: (1) atomic emission spectroscopies which require the generation of plasmas through laser-induced breakdown, electrical arcing, or similar means; (2) non-spectroscopic methods which measure one or more physical properties (e.g., mass, thermal conductivity, density). In this report, we present our progress during Fiscal Year 2011 (FY11) in the research and development of a non-spectroscopic method for noble gas detection. During Fiscal Year 2010 (FY10), we demonstrated via proof-of-concept experiments that the combination of thermal conductivity detection (TCD) and coating-free damped resonance detection (CFDRD) using micro-electromechanical systems (MEMS) could provide selective sensing of these inert species. Since the MEMS-based TCD technology was directly adapted from a brassboard prototype commissioned by a previous chemical sensing project, FY11 efforts focused on advancing the state of the newer CFDRD method. This work, guided by observations previously reported in the open literature, has not only

  12. 2.45 GHz Rectenna Designed for Wireless Sensors Operating at 500 C

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Schwartz, Zachary D.; Jordan, Jennifer L.; Downey, Alan N.; Neudeck, Philip G.

    2004-01-01

    High temperature wireless sensors that operate at 500 C are required for aircraft engine monitoring and performance improvement These sensors would replace currently used hard-wired sensors and lead to a substantial reduction in mass. However, even if the sensor output data is transmitted wirelessly to a receiver in the cooler part of the engine, and the associated cables are eliminated, DC power cables are still required to operate the sensors and power the wireless circuits. To solve this problem, NASA is developing a rectenna, a circuit that receives RF power and converts it to DC power. The rectenna would be integrated with the wireless sensor, and the RF transmitter that powers the rectenna would be located in the cooler part of the engine. In this way, no cables to or from the sensors are required. Rectennas haw been demonstrated at ambient room temperature, but to date, no high temperature rectennas haw been reported. In this paper, we report the first rectenna designed for 2.45 GHz operation at 500 C. The circuit consists of a microstrip dipole antenna, a stripline impedance matching circuit, and a stripline low pass filter to prevent transmission of higher harmonics created by the rectifying diode fabricated on an Alumina substrate. The rectifying diode is the gate to source junction of a 6H Sic MESFET and the capacitor and load resistor are chip elements that are each bonded to the Alumina substrate. Each element and the hybrid, rectenna circuit haw been characterized through 500 C.

  13. An open communication and sensor platform for urban search and rescue operations

    NASA Astrophysics Data System (ADS)

    Korkalainen, Marko; Mäyrä, Aki P.; Känsälä, Klaus

    2012-10-01

    In this paper, we present research results carried out in EU funded project SGL for USaR (Second Generation Locator for Urban Search and Rescue Operations). The project aims to develop wireless standalone communication system with embedded sensor network, which is targeted to detect signs of life, locate victims in disaster areas and detect hazards. The system consists of REDS (Remote Early Detection System) wireless sensor network and FIRST portable first responder device integrating 5 different victim location methods. REDS has wireless CO and CO2 sensors, a camera, vibration sensors and a sound sensor for detection of life signs. The system provides also a pointing device to locate objects on the search area. Victim positioning is possible with GPS and radio based time of flight methods. Portable and user operated FIRST device combines field chemical, audio and video measurements for early location of entrapped people, detection of buried people, air quality monitoring in confined spaces and safety and security monitoring. The system level communication is divided in two levels: sensor network level uses short range local communication and communication hubs, which use long range high level communication with operation command centre. During the project, implemented REDS sensor network and FIRST device have been tested on a field conditions and they have proven to be robust and reliable.

  14. Weighted Global Artificial Bee Colony Algorithm Makes Gas Sensor Deployment Efficient

    PubMed Central

    Jiang, Ye; He, Ziqing; Li, Yanhai; Xu, Zhengyi; Wei, Jianming

    2016-01-01

    This paper proposes an improved artificial bee colony algorithm named Weighted Global ABC (WGABC) algorithm, which is designed to improve the convergence speed in the search stage of solution search equation. The new method not only considers the effect of global factors on the convergence speed in the search phase, but also provides the expression of global factor weights. Experiment on benchmark functions proved that the algorithm can improve the convergence speed greatly. We arrive at the gas diffusion concentration based on the theory of CFD and then simulate the gas diffusion model with the influence of buildings based on the algorithm. Simulation verified the effectiveness of the WGABC algorithm in improving the convergence speed in optimal deployment scheme of gas sensors. Finally, it is verified that the optimal deployment method based on WGABC algorithm can improve the monitoring efficiency of sensors greatly as compared with the conventional deployment methods. PMID:27322262

  15. Detection of acetone in exhaled breath with the use of micropreconcentrator and a commercial gas sensor

    NASA Astrophysics Data System (ADS)

    Michoń, Dagmara; Rydosz, Artur; Domański, Krzysztof; Maziarz, Wojciech; Pisarkiewicz, Tadeusz

    2016-12-01

    This paper presents investigation results obtained with the measuring system enabling detection of acetone with concentrations lower than 1 ppm. In the experiment we used both conventional preconcentrators made from materials such as stainless steel and quartz tubes and a micropreconcentrator manufactured in MEMS technology. The active volume of all preconcentrators was equal to enable comparisons of their performance. As a gas detector at the output of the measurement system we used both commercial semiconductor gas sensor and a mass spectrometer for comparison purposes. The obtained results show that the measurement system with micropreconcentrator and a commercial gas sensor can be used for detection of low level acetone present in the air exhaled by diabetics.

  16. Effect of electrode gap on the sensing properties of multiwalled carbon nanotubes based gas sensor

    NASA Astrophysics Data System (ADS)

    Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif

    2016-11-01

    Vertically aligned multiwalled carbon nanotubes (MWCNT) were grown on Si substrate coated with alumina and iron using chemical vapor deposition. Electrode gap of 10, 25 and 50 µm were adopted to determine the effect of varying gap spacing on the sensing properties such as voltage breakdown, sensitivity and selectivity for three gases namely argon, carbon dioxide and ammonia. Argon has the lowest voltage breakdown for every electrode gap. The fabricated MWCNT based gas sensor drastically reduced the voltage breakdown by 89.5% when the electrode spacing is reduced from 50 µm to 10 µm. The reduction is attributed to the high non-uniform electric field between the electrodes caused by the protrusion of nanotips. The sensor shows good sensitivity and selectivity with the ability to detect the gas in the mixture with air provided that the concentration is ≥ 20% where the voltage breakdown will be close to the pure gas.

  17. Global Coverage Measurement Planning Strategies for Mobile Robots Equipped with a Remote Gas Sensor

    PubMed Central

    Arain, Muhammad Asif; Trincavelli, Marco; Cirillo, Marcello; Schaffernicht, Erik; Lilienthal, Achim J.

    2015-01-01

    The problem of gas detection is relevant to many real-world applications, such as leak detection in industrial settings and landfill monitoring. In this paper, we address the problem of gas detection in large areas with a mobile robotic platform equipped with a remote gas sensor. We propose an algorithm that leverages a novel method based on convex relaxation for quickly solving sensor placement problems, and for generating an efficient exploration plan for the robot. To demonstrate the applicability of our method to real-world environments, we performed a large number of experimental trials, both on randomly generated maps and on the map of a real environment. Our approach proves to be highly efficient in terms of computational requirements and to provide nearly-optimal solutions. PMID:25803707

  18. Global coverage measurement planning strategies for mobile robots equipped with a remote gas sensor.

    PubMed

    Arain, Muhammad Asif; Trincavelli, Marco; Cirillo, Marcello; Schaffernicht, Erik; Lilienthal, Achim J

    2015-03-20

    The problem of gas detection is relevant to many real-world applications, such as leak detection in industrial settings and landfill monitoring. In this paper, we address the problem of gas detection in large areas with a mobile robotic platform equipped with a remote gas sensor. We propose an algorithm that leverages a novel method based on convex relaxation for quickly solving sensor placement problems, and for generating an efficient exploration plan for the robot. To demonstrate the applicability of our method to real-world environments, we performed a large number of experimental trials, both on randomly generated maps and on the map of a real environment. Our approach proves to be highly efficient in terms of computational requirements and to provide nearly-optimal solutions.

  19. Geo-mechanical Model Testing for Stability of Underground Gas Storage in Halite During the Operational Period

    NASA Astrophysics Data System (ADS)

    Chen, Xuguang; Zhang, Qiangyong; Li, Shucai; Liu, Dejun

    2016-07-01

    A 3D geo-mechanical model test is conducted to study the stability of underground gas storage in halite, modeled after the Jintan gas storage constructed in bedded salt rock in China. A testing apparatus is developed to generate long-term stable trapezoid geostresses onto the model cavity, corresponding to the actual gas storage cavern. The time-depending character of the material is simulated using a rheological material, which was tested using a self-developed apparatus. The model cavern is built using an ellipsoid wooden mold divided into small blocks which are assembled and placed into the designed position during the model construction. They are then pulled out one by one to form the cavern. The ellipsoid cavern wall is then lined within a latex balloon. Gas is injected into the cavity and extracted to simulate the operational process of gas injection and recovery. Optical sensors embedded into the model to measure the displacement around the cavity showed that the largest deformation occurs in the middle section of the cavity. The deformation rate increases with increasing gas pressure. At 11 MPa the cavity is in equilibrium with the geostress. The pressure is highest during the gas recovery stages, indicating that gas recovery can threaten the cavern's operational stability, while high gas injection causes rock mass compression and deformation outward from the cavern. The deformation is the combination of cavern convergence and gas-induced rebound which leads to tensile and compression during gas injection and recovery. Hence, the fatigue properties of salt rock should be studied further.

  20. MWCNT-polymer composites as highly sensitive and selective room temperature gas sensors.

    PubMed

    Mangu, Raghu; Rajaputra, Suresh; Singh, Vijay P

    2011-05-27

    Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si/SiO(2) substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the composite films. These sensors exhibited excellent response and selectivity at room temperature when exposed to low concentrations (100 ppm) of analyte gases like NH(3) and NO(2). The effect of various solvents on the sensor response imparting selectivity to CNT-polymer nanocomposites was investigated extensively. Sensitivities as high as 28% were observed for an MWCNT-PEDOT:PSS composite sensor when exposed to 100 ppm of NH(3) and - 29.8% sensitivity for an MWCNT-PANI composite sensor to 100 ppm of NO(2) when DMSO was used as a solvent. Additionally, the sensors exhibited good reversibility.

  1. Towards sustainability in offshore oil and gas operations

    NASA Astrophysics Data System (ADS)

    Khan, M. Ibrahim

    acceptable, economically profitable and socially responsible. This dissertation discusses the framework of true 'sustainability' for practically all aspects oil and gas operations and nature-based resource operations. Sustainability of existing offshore oil and gas operations techniques are analyzed and new nature-based technologies are proposed. Also evaluated are the fate and effect, environmental impact, risk factors, and the green supply chain in the case of seismic, drilling, production and decommissioning of oil operations. It is demonstrated with detailed examples that using the new approach will be economically more beneficial than the conventional approach, even in the short-term. The dissertation also examines the present status of petroleum operations with respect to waste generation, improper resource management, and the usage of toxic compounds in the overall lifecycle. To achieve true sustainability, some innovative models and technologies are presented. They include achievement of zero emissions, zero waste of resources, zero waste in activities, zero use of toxics, and zero waste in product life-cycle. This dissertation also discusses the environmental and technological problems of the petroleum sector and provides guidelines to achieve overall sustainability in oil company activities. Finally, this dissertation shows that inherent sustainability can be achieved by the involvement of community participation. The new screening tool proposed in this dissertation provides proper guidelines to achieve true sustainability in the technology development and other resource development operations.

  2. Vector magnetometry sensor for internal inspection of gas distribution mains. Final report, February 1995-August 1996

    SciTech Connect

    Farra, R.; Fowler, T.

    1997-06-01

    There is a recognized need for an advanced distribution pipe inspection system which can operate in 4` and 6` diameter pipes. This program developed a prototype sensor car based on vector magnetometry. The prototype sensor system was tested in the laboratory. Test data is presented showing defect detection capability for defects as small as 25% of the pipe wall. Field tests were also conducted with mixed results. Varying corrosion levels were observed. However, specific defects were difficult to identify.

  3. Gas Release During Saltwell Pumping: Interpretation of Operational Data

    SciTech Connect

    J.L. Huckaby; L.M. Peurrung; P.A. Gauglitz

    1999-09-16

    The Hanford Site has 149 single-shell tanks (SSTs) containing radioactive waste that is a complex mix of radioactive and chemical products. Of these, 67 are known or suspected to have leaked liquid into the surrounding soil, while 82 are considered sound (Hanlon 1999). To minimize the amount of material that potentially could leak into the surrounding soil, all of the SSTs are scheduled to have drainable liquid removed and to be designated as interim stabilized. Of the SSTs, 119 have been declared stabilized, and only 30 require further processing (Hanlon 1999). Many of the tanks have been declared stabilized administratively, with only 45 tanks having had drainable liquid removed. The pending consent decree between the Washington State Department of Ecology and the Office of River Protection. (U.S. District Court Eastern District of Washington, 1999) sets a milestone to complete interim stabilization by September 2004. While process equipment exists for removing drainable liquid, and its operation is well known from previous pumping campaigns, a number of safety issues associated with the release and potential ignition of flammable gases within the tanks needs to be addressed. The safety concerns associated with flammable gases stem from the observation that some of the waste in the SSTs generates and retains hazardous quantities of flammable gases, including hydrogen, nitrous oxide, and ammonia. Of the 30 SSTs remaining to be declared interim stabilized, 29 need to have drainable liquid removed by saltwell pumping (waste in tank 241-C-106 will be removed by sluicing), and 16 of these are on the Flammable Gas Watch List (FGWL) (Hopkins 1995; Hanlon 1999). Most of these tanks are in Facility Group 2 (Noorani 1997); that is, it is believed that tank operations may induce the release of significant quantities of flammable gas, but gas release does not occur spontaneously. In particular, saltwell pumping to remove the interstitial liquid from SSTs is expected to cause

  4. Gas Sensors Characterization and Multilayer Perceptron (MLP) Hardware Implementation for Gas Identification Using a Field Programmable Gate Array (FPGA)

    PubMed Central

    Benrekia, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

    2013-01-01

    This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

  5. Two-dimensional electron gas magnetic field sensors

    NASA Astrophysics Data System (ADS)

    Heremans, J.; Partin, D. L.; Morelli, D. T.; Fuller, B. K.; Thrush, C. M.

    1990-07-01

    We describe the use of accumulation layers of electron charge in applications as magnetoresistive devices. We consider two such systems: an InGaAs/InP heterostructure in which we identify a two-dimensional electron gas from the observation of the quantum Hall effect, and InAs films, in which a strong surface accumulation of charge is inferred from depth profiling studies of the galvanomagnetic coefficients. Magnetoresistive devices fabricated from these materials exhibit outstanding field sensitivity and temperature stability due to the existence of electrons of relatively high density and mobility in the accumulation regions. We also model the magnetosensitivity of our devices.

  6. Single molecular transistor as a superior gas sensor

    NASA Astrophysics Data System (ADS)

    Ray, S. J.

    2015-07-01

    Single Molecular Transistor (SMT) is known for its quantised nature of transport which can be used for sensing purposes. In this work, a SMT device prototype has been proposed for chemical sensing application, which is sensitive at the single molecular level. The operational methodology and performance have been investigated using first-principles calculations within a density functional theory framework. The charge stability diagram carries unique signature of the molecule present within the SMT and this property can be used to detect the presence of an individual molecule from a mixture of different molecules. Details about the possible experimental realisation of such a device has been discussed. The present approach provides a unique combination of very simple design with operation, perfect gate-island coupling, large temperature range of operation and extremely high detection sensitivity.

  7. Model operating permits for natural gas processing plants

    SciTech Connect

    Arend, C.

    1995-12-31

    Major sources as defined in Title V of the Clean Air Act Amendments of 1990 that are required to submit an operating permit application will need to: Evaluate their compliance status; Determine a strategic method of presenting the general and specific conditions of their Model Operating Permit (MOP); Maintain compliance with air quality regulations. A MOP is prepared to assist permitting agencies and affected facilities in the development of operating permits for a specific source category. This paper includes a brief discussion of example permit conditions that may be applicable to various types of Title V sources. A MOP for a generic natural gas processing plant is provided as an example. The MOP should include a general description of the production process and identify emission sources. The two primary elements that comprise a MOP are: Provisions of all existing state and/or local air permits; Identification of general and specific conditions for the Title V permit. The general provisions will include overall compliance with all Clean Air Act Titles. The specific provisions include monitoring, record keeping, and reporting. Although Title V MOPs are prepared on a case-by-case basis, this paper will provide a general guideline of the requirements for preparation of a MOP. Regulatory agencies have indicated that a MOP included in the Title V application will assist in preparation of the final permit provisions, minimize delays in securing a permit, and provide support during the public notification process.

  8. Monitoring System for Farming Operations with Wearable Devices Utilized Sensor Networks

    PubMed Central

    Fukatsu, Tokihiro; Nanseki, Teruaki

    2009-01-01

    In order to automatically monitor farmers’ activities, we propose a farm operation monitoring system using “Field Servers” and a wearable device equipped with an RFID reader and motion sensors. Our proposed system helps in recognizing farming operations by analyzing the data from the sensors and detected RFID tags that are attached to various objects such as farming materials, facilities, and machinery. This method can be applied to various situations without changing the conventional system. Moreover, this system provides useful information in real-time and controls specific machines in a coordinated manner on the basis of recognized operation. PMID:22454578

  9. Job-Oriented Basic Skills (JOBS) Program for the Acoustic Sensor Operations Strand.

    ERIC Educational Resources Information Center

    U'Ren, Paula Kabance; Baker, Meryl S.

    An effort was undertaken to develop a job-oriented basic skills curriculum appropriate for the acoustic sensor operations area, which includes members of four ratings: ocean systems technician, aviation antisubmarine warfare operator, sonar technician (surface), and sonar technician (submarine). Analysis of the job duties of the four ratings…

  10. Evaluation of a Trainer for Sensor Operators on Gunship II Aircraft.

    ERIC Educational Resources Information Center

    Cream, Bertram W.

    This report describes the design, development, and evaluation of a training device intended to enable ground-based practice of equipment operation and target-tracking skills that are required by the Forward-Looking Infrared (FLIR) and Low Light Level TV (LLLTV) sensor operators assigned to Gunship II aircraft. This trainer makes use of a…

  11. Gas Sensors Based on Tin Oxide Nanoparticles Synthesized from a Mini-Arc Plasma Source

    DOE PAGES

    Lu, Ganhua; Huebner, Kyle L.; Ocola, Leonidas E.; ...

    2006-01-01

    Minimore » aturized gas sensors or electronic noses to rapidly detect and differentiate trace amount of chemical agents are extremely attractive. In this paper, we report on the fabrication and characterization of a functional tin oxide nanoparticle gas sensor. Tin oxide nanoparticles are first synthesized using a convenient and low-cost mini-arc plasma source. The nanoparticle size distribution is measured online using a scanning electrical mobility spectrometer (SEMS). The product nanoparticles are analyzed ex-situ by high resolution transmission electron microscopy (HRTEM) for morphology and defects, energy dispersive X-ray (EDX) spectroscopy for elemental composition, electron diffraction for crystal structure, and X-ray photoelectron spectroscopy (XPS) for surface composition. Nonagglomerated rutile tin oxide ( SnO 2 ) nanoparticles as small as a few nm have been produced. Larger particles bear a core-shell structure with a metallic core and an oxide shell. The nanoparticles are then assembled onto an e-beam lithographically patterned interdigitated electrode using electrostatic force to fabricate the gas sensor. The nanoparticle sensor exhibits a fast response and a good sensitivity when exposed to 100 ppm ethanol vapor in air.« less

  12. Solution-Processed Gas Sensors Employing SnO2 Quantum Dot/MWCNT Nanocomposites.

    PubMed

    Liu, Huan; Zhang, Wenkai; Yu, Haoxiong; Gao, Liang; Song, Zhilong; Xu, Songman; Li, Min; Wang, Yang; Song, Haisheng; Tang, Jiang

    2016-01-13

    Solution-processed SnO2 colloidal quantum dots (CQDs) have emerged as an important new class of gas-sensing materials due to their potential for low-cost and high-throughput fabrication. Here we employed the design strategy based on the synergetic effect from highly sensitive SnO2 CQDs and excellent conductive properties of multiwalled carbon nanotubes (MWCNTs) to overcome the transport barrier in CQD gas sensors. The attachment and coverage of SnO2 CQDs on the MWCNT surfaces were achieved by simply mixing the presynthesized SnO2 CQDs and MWCNTs at room temperature. Compared to the pristine SnO2 CQDs, the sensor based on SnO2 quantum dot/MWCNT nanocomposites exhibited a higher response upon exposure to H2S, and the response toward 50 ppm of H2S at 70 °C was 108 with the response and recovery time being 23 and 44 s. Because of the favorable energy band alignment, the MWCNTs can serve as the acceptor of the electrons that are injected from H2S into SnO2 quantum dots in addition to the charge transport highway to direct the electron flow to the electrode, thereby enhancing the sensor response. Our research results open an easy pathway for developing highly sensitive and low-cost gas sensors.

  13. Fiber-optic photo-acoustic spectroscopy sensor for harsh environment gas detection

    NASA Astrophysics Data System (ADS)

    Wu, Juntao; Deng, Kung-Li; Guida, Renato; Lee, Boon

    2007-09-01

    Photo-acoustic spectroscopy (PAS) has been successfully applied to detect various gases and chemicals due to its high selectivity and sensitivity. However, the performance of the conventional acoustic sensors prohibits the application of PAS for harsh environment gas species real-time monitoring. By replacing conventional acoustic sensors, such as microphone and piezo-transducers, with a high-temperature Fiber Bragg Grating (FBG) vibration sensor, we developed a fiber-optic PAS sensing system that can be used in high-temperature and high-pressure harsh environments for gas species identification and concentration measurement. A resonant acoustic chamber is designed, and FBG vibration sensor is embedded in the molybdenum membrane. An OPO laser is used for spectrum scanning. Preliminary test on water vapor has been conducted, and the result is analyzed. This sensing technology can be adapted into harsh environments, such as Integrated Gasification Combined Cycle (IGCC) power plant, and provide on-line real-time monitoring of gases species, such as CO, H IIO, and O II. Presently, our FBG-based vibration sensor can withstand the high temperature up to 800°C.

  14. Modeling and experimental study on characterization of micromachined thermal gas inertial sensors.

    PubMed

    Zhu, Rong; Ding, Henggao; Su, Yan; Yang, Yongjun

    2010-01-01

    Micromachined thermal gas inertial sensors based on heat convection are novel devices that compared with conventional micromachined inertial sensors offer the advantages of simple structures, easy fabrication, high shock resistance and good reliability by virtue of using a gaseous medium instead of a mechanical proof mass as key moving and sensing elements. This paper presents an analytical modeling for a micromachined thermal gas gyroscope integrated with signal conditioning. A simplified spring-damping model is utilized to characterize the behavior of the sensor. The model relies on the use of the fluid mechanics and heat transfer fundamentals and is validated using experimental data obtained from a test-device and simulation. Furthermore, the nonideal issues of the sensor are addressed from both the theoretical and experimental points of view. The nonlinear behavior demonstrated in experimental measurements is analyzed based on the model. It is concluded that the sources of nonlinearity are mainly attributable to the variable stiffness of the sensor system and the structural asymmetry due to nonideal fabrication.

  15. Intrinsic fiber optical gas sensor based on surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Niggemann, Matthias; Katerkamp, Andreas; Pellmann, Maria; Bolsmann, Peter; Reinbold, Joerg; Cammann, Karl

    1995-09-01

    A miniaturized fiber optical sensor based on surface plasmon resonance spectroscopy is investigated in view of the detection of organic solvent vapors, particularly tetrachloroethene. Surface plasmons are excited on a silver coated multimode fiber by polychromatic light, and the resonant excitation is detected as a resonant absorption band in the measured output spectrum. When the analyte is absorbed in a thin gas-sensitive polysiloxane film deposited on the silver layer the polymer film changes its thickness and its refractive index. These changes result in a wavelength shift of the resonant curve depending on the analyte gas concentration. Theoretical considerations about the sensing effect are made and resonance curves were computer-simulated. Based on this simulation the layout of all sensor parameters was optimized. The sensor shows an excellent response to tetrachloroethene with a response time of two seconds and high reporducibility. Using self-assembling monolayers on the silver surface a long-term stability of more than three months is obtained. The sensor shows low cross sensitivities less than 1% to other solvent vapors like aceton and ethanol, furthermore, the influence of humidity is very low. This miniaturized fiber optical sensor in combination with an easy-to-handle and non-sophisticated measuring and evaluation unit is excellently suitable for the remote sensing of special organic solvent vapors.

  16. Rational design of sub-parts per million specific gas sensors array based on metal nanoparticles decorated nanowire enhancement-mode transistors.

    PubMed

    Zou, Xuming; Wang, Jingli; Liu, Xingqiang; Wang, Chunlan; Jiang, Ying; Wang, Yong; Xiao, Xiangheng; Ho, Johnny C; Li, Jinchai; Jiang, Changzhong; Fang, Ying; Liu, Wei; Liao, Lei

    2013-07-10

    "One key to one lock" hybrid sensor configuration is rationally designed and demonstrated as a direct effective route for the target-gas-specific, highly sensitive, and promptly responsive chemical gas sensing for room temperature operation in a complex ambient background. The design concept is based on three criteria: (i) quasi-one-dimensional metal oxide nanostructures as the sensing platform which exhibits good electron mobility and chemical and thermal stability; (ii) deep enhancement-mode field-effect transistors (E-mode FETs) with appropriate threshold voltages to suppress the nonspecific sensitivity to all gases (decouple the selectivity and sensitivity away from nanowires); (iii) metal nanoparticle decoration onto the nanostructure surface to introduce the gas specific selectivity and sensitivity to the sensing platform. In this work, using Mg-doped In2O3 nanowire E-mode FET sensor arrays decorated with various discrete metal nanoparticles (i.e., Au, Ag, and Pt) as illustrative prototypes here further confirms the feasibility of this design. Particularly, the Au decorated sensor arrays exhibit more than 3 orders of magnitude response to the exposure of 100 ppm CO among a mixture of gases at room temperature. The corresponding response time and detection limit are as low as ∼4 s and ∼500 ppb, respectively. All of these could have important implications for this "one key to one lock" hybrid sensor configuration which potentially open up a rational avenue to the design of advanced-generation chemical sensors with unprecedented selectivity and sensitivity.

  17. Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS.

    PubMed

    Wada, Takahiro; Murata, Naoyoshi; Uehara, Hiromitsu; Suzuki, Takuya; Nitani, Hiroaki; Niwa, Yasuhiro; Uo, Motohiro; Asakura, Kiyotaka

    2016-03-14

    Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by μ-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a freshly prepared sensor, all Pd species were in the PdO form; in a heavily deteriorated sensor, Pd/Al2O3 in the external region changed to metallic Pd particles, while the PdO structure in the inner region near the heater remained unchanged. The Pd species distribution was in agreement with the simulated thermal distribution. Temperature control was crucial to maintain the high performance of the gas sensor. The improved sensor allows homogeneous heating and has a lifetime of more than 5 years.

  18. Gas mixture studies for streamer operated Resistive Plate Chambers

    NASA Astrophysics Data System (ADS)

    Paoloni, A.; Longhin, A.; Mengucci, A.; Pupilli, F.; Ventura, M.

    2016-06-01

    Resistive Plate Chambers operated in streamer mode are interesting detectors in neutrino and astro-particle physics applications (like OPERA and ARGO experiments). Such experiments are typically characterized by large area apparatuses with no stringent requirements on detector aging and rate capabilities. In this paper, results of cosmic ray tests performed on a RPC prototype using different gas mixtures are presented, the principal aim being the optimization of the TetraFluoroPropene concentration in Argon-based mixtures. The introduction of TetraFluoroPropene, besides its low Global Warming Power, is helpful because it simplifies safety requirements allowing to remove also isobutane from the mixture. Results obtained with mixtures containing SF6, CF4, CO2, N2 and He are also shown, presented both in terms of detectors properties (efficiency, multiple-streamer probability and time resolution) and in terms of streamer characteristics.

  19. Chlorine gas sensors using one-dimensional tellurium nanostructures.

    PubMed

    Sen, Shashwati; Sharma, Madhvi; Kumar, Vivek; Muthe, K P; Satyam, P V; Bhatta, Umananda M; Roy, M; Gaur, N K; Gupta, S K; Yakhmi, J V

    2009-03-15

    Tellurium nanotubes have been grown by physical vapor deposition under inert environment at atmospheric pressure as well as under vacuum conditions. Different techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical absorption have been utilized for characterization of grown structures. Films prepared using both types of tellurium nanotubes were characterized for sensitivity to oxidizing and reducing gases and it was found that the relative response to gases depends on the microstructure. Nanotubes prepared at atmospheric pressure (of argon) showed high sensitivity and better selectivity to chlorine gas. Impedance spectroscopy studies showed that the response to chlorine is mainly contributed by grain boundaries and is therefore enhanced for nanotubes prepared under argon atmosphere.

  20. ZnO nanoparticles based fiber optic gas sensor

    NASA Astrophysics Data System (ADS)

    Narasimman, S.; Balakrishnan, L.; Meher, S. R.; Sivacoumar, R.; Alex, Z. C.

    2016-05-01

    In this work, ZnO nanoparticles were synthesized by simple aqueous chemical route method. The synthesized ZnO nanoparticles were characterized by X-ray diffraction andscanning electron microscope. The sensitivity of the nanoparticles was studied for different gases like acetone, ammonia andethanol in terms of variation in spectral light intensity. The XRD and SEM analysis confirms the formation of hexagonal wurtzite structure with the grain size of 11.2 nm. The small cladding region of the optical fiber was replaced with the synthesized nanoparticles. The light spectrum was recorded for different gas concentrations. The synthesized nanoparticles showed high sensitivity towards ammonia in low ppm level and acetone in high ppm level.