Wafer-Level Vacuum Packaging of Smart Sensors

PubMed Central

Hilton, Allan; Temple, Dorota S.

2016-01-01

The reach and impact of the Internet of Things will depend on the availability of low-cost, smart sensors—“low cost” for ubiquitous presence, and “smart” for connectivity and autonomy. By using wafer-level processes not only for the smart sensor fabrication and integration, but also for packaging, we can further greatly reduce the cost of sensor components and systems as well as further decrease their size and weight. This paper reviews the state-of-the-art in the wafer-level vacuum packaging technology of smart sensors. We describe the processes needed to create the wafer-scale vacuum microchambers, focusing on approaches that involve metal seals and that are compatible with the thermal budget of complementary metal-oxide semiconductor (CMOS) integrated circuits. We review choices of seal materials and structures that are available to a device designer, and present techniques used for the fabrication of metal seals on device and window wafers. We also analyze the deposition and activation of thin film getters needed to maintain vacuum in the ultra-small chambers, and the wafer-to-wafer bonding processes that form the hermetic seal. We discuss inherent trade-offs and challenges of each seal material set and the corresponding bonding processes. Finally, we identify areas for further research that could help broaden implementations of the wafer-level vacuum packaging technology. PMID:27809249

Accelerator Vacuum Protection System

NASA Astrophysics Data System (ADS)

Barua, Pradip; Kothari, Ashok; Archunan, M.; Joshi, Rajan

2012-11-01

A new and elaborate automatic vacuum protection system using fast acting valve has been installed to avoid accidental venting of accelerator from experimental chamber side. To cover all the beam lines and to reduce the system cost, it has been installed at a common point from where all the seven beam lines originate. The signals are obtained by placing fast response pressure sensing gauges (HV SENSOR) near all the experimental stations. The closing time of the fast valve is 10 milli-second. The fast closing system protects only one vacuum line at a time. At IUAC, we have seven beam lines so one sensor was placed in each of the beam lines near experimental chamber and a multiplexer was incorporated into the fast closing system. At the time of experiment, the sensor of the active beam line is selected through the multiplexer and the Fast closing valve is interlocked with the selected sensor. As soon as the pressure sensor senses the pressure rise beyond a selected pressure, the signal is transferred and the fast valve closes within 10 to 12 millisecond.

Phacoemulsification tip vacuum pressure: Comparison of 4 devices.

PubMed

Payne, Marielle; Georgescu, Dan; Waite, Aaron N; Olson, Randall J

2006-08-01

To determine the vacuum pressure generated by 4 phacoemulsification devices measured at the phacoemulsification tip. University ophthalmology department. The effective vacuum pressures generated by the Sovereign (AMO), Millennium (Bausch & Lomb), Legacy AdvanTec (Alcon Laboratories), and Infiniti (Alcon Laboratories) phacoemulsification machines were measured with a device that isolated the phacoemulsification tip in a chamber connected to a pressure gauge. The 4 machines were tested at multiple vacuum limit settings, and the values were recorded after the foot pedal was fully depressed and the pressure had stabilized. The AdvanTec and Infiniti machines were tested with and without occlusion of the Aspiration Bypass System (ABS) side port (Alcon Laboratories). The Millennium machine was tested using venturi and peristaltic pumps. The machines generated pressures close to the expected at maximum vacuum settings between 100 mm Hg and 500 mm Hg with few intermachine variations. There was no significant difference between pressures generated using 19- or 20-gauge tips (Millennium and Sovereign). The addition of an ABS side port decreased vacuum by a mean of 12.1% (P < .0001). Although there were some variations in vacuum pressures among phacoemulsification machines, particularly when an aspiration bypass tip was used, these discrepancies are probably not clinically significant.

Development of a real-time monitoring system for intra-fractional motion in intracranial treatment using pressure sensors.

PubMed

Inata, Hiroki; Araki, Fujio; Kuribayashi, Yuta; Hamamoto, Yasushi; Nakayama, Shigeki; Sodeoka, Noritaka; Kiriyama, Tetsukazu; Nishizaki, Osamu

2015-09-21

This study developed a dedicated real-time monitoring system to detect intra-fractional head motion in intracranial radiotherapy using pressure sensors. The dedicated real-time monitoring system consists of pressure sensors with a thickness of 0.6 mm and a radius of 9.1 mm, a thermoplastic mask, a vacuum pillow, and a baseplate. The four sensors were positioned at superior-inferior and right-left sides under the occipital area. The sampling rate of pressure sensors was set to 5 Hz. First, we confirmed that the relationship between the force and the displacement of the vacuum pillow follows Hook's law. Next, the spring constant for the vacuum pillow was determined from the relationship between the force given to the vacuum pillow and the displacement of the head, detected by Cyberknife target locating system (TLS) acquisitions in clinical application. Finally, the accuracy of our system was evaluated by using the 2  ×  2 confusion matrix. The regression lines between the force, y, and the displacement, x, of the vacuum pillow were given by y = 3.8x, y = 4.4x, and y = 5.0x when the degree of inner pressure was  -12 kPa,-20 kPa, and  -27 kPa, respectively. The spring constant of the vacuum pillow was 1.6 N mm(-1) from the 6D positioning data of a total of 2999 TLS acquisitions in 19 patients. Head motions of 1 mm, 1.5 mm, and 2 mm were detected in real-time with the accuracies of 67%, 84%, and 89%, respectively. Our system can detect displacement of the head continuously during every interval of TLS with a resolution of 1-2 mm without any radiation exposure.

46 CFR 154.1335 - Pressure and vacuum protection.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Pressure and vacuum protection. 154.1335 Section 154... Equipment Instrumentation § 154.1335 Pressure and vacuum protection. (a) Each cargo tank must have the following: (1) A pressure gauge that: (i) Monitors the vapor space; (ii) Is readable at the tank; and (iii...

Measurement of vacuum pressure with a magneto-optical trap: A pressure-rise method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Rowan W. G.; Lee, Lucie A.; Findlay, Elizabeth A.

2015-09-15

The lifetime of an atom trap is often limited by the presence of residual background gases in the vacuum chamber. This leads to the lifetime being inversely proportional to the pressure. Here, we use this dependence to estimate the pressure and to obtain pressure rate-of-rise curves, which are commonly used in vacuum science to evaluate the performance of a system. We observe different rates of pressure increase in response to different levels of outgassing in our system. Therefore, we suggest that this is a sensitive method which will find useful applications in cold atom systems, in particular, where the inclusionmore » of a standard vacuum gauge is impractical.« less

33 CFR 159.111 - Pressure and vacuum pulse test.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Pressure and vacuum pulse test... (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.111 Pressure and vacuum pulse test. Liquid retention components of the device with manufacturer specified venting...

33 CFR 159.111 - Pressure and vacuum pulse test.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Pressure and vacuum pulse test... (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.111 Pressure and vacuum pulse test. Liquid retention components of the device with manufacturer specified venting...

33 CFR 159.111 - Pressure and vacuum pulse test.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Pressure and vacuum pulse test... (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.111 Pressure and vacuum pulse test. Liquid retention components of the device with manufacturer specified venting...

Capacitance pressure sensor

DOEpatents

Eaton, William P.; Staple, Bevan D.; Smith, James H.

2000-01-01

A microelectromechanical (MEM) capacitance pressure sensor integrated with electronic circuitry on a common substrate and a method for forming such a device are disclosed. The MEM capacitance pressure sensor includes a capacitance pressure sensor formed at least partially in a cavity etched below the surface of a silicon substrate and adjacent circuitry (CMOS, BiCMOS, or bipolar circuitry) formed on the substrate. By forming the capacitance pressure sensor in the cavity, the substrate can be planarized (e.g. by chemical-mechanical polishing) so that a standard set of integrated circuit processing steps can be used to form the electronic circuitry (e.g. using an aluminum or aluminum-alloy interconnect metallization).

46 CFR 30.10-55 - Pressure vacuum relief valve-TB/ALL.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 1 2011-10-01 2011-10-01 false Pressure vacuum relief valve-TB/ALL. 30.10-55 Section 30... Definitions § 30.10-55 Pressure vacuum relief valve—TB/ALL. The term pressure vacuum relief valve means any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of...

46 CFR 30.10-55 - Pressure vacuum relief valve-TB/ALL.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 1 2014-10-01 2014-10-01 false Pressure vacuum relief valve-TB/ALL. 30.10-55 Section 30... Definitions § 30.10-55 Pressure vacuum relief valve—TB/ALL. The term pressure vacuum relief valve means any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of...

46 CFR 30.10-55 - Pressure vacuum relief valve-TB/ALL.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 1 2010-10-01 2010-10-01 false Pressure vacuum relief valve-TB/ALL. 30.10-55 Section 30... Definitions § 30.10-55 Pressure vacuum relief valve—TB/ALL. The term pressure vacuum relief valve means any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of...

46 CFR 30.10-55 - Pressure vacuum relief valve-TB/ALL.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 1 2012-10-01 2012-10-01 false Pressure vacuum relief valve-TB/ALL. 30.10-55 Section 30... Definitions § 30.10-55 Pressure vacuum relief valve—TB/ALL. The term pressure vacuum relief valve means any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of...

46 CFR 30.10-55 - Pressure vacuum relief valve-TB/ALL.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 1 2013-10-01 2013-10-01 false Pressure vacuum relief valve-TB/ALL. 30.10-55 Section 30... Definitions § 30.10-55 Pressure vacuum relief valve—TB/ALL. The term pressure vacuum relief valve means any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of...

Cryogenic High Pressure Sensor Module

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams, Qamar A. (Inventor); Powers, William T. (Inventor)

1999-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Cryogenic, Absolute, High Pressure Sensor

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

2001-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Additive manufacturing of magnetic shielding and ultra-high vacuum flange for cold atom sensors.

PubMed

Vovrosh, Jamie; Voulazeris, Georgios; Petrov, Plamen G; Zou, Ji; Gaber, Youssef; Benn, Laura; Woolger, David; Attallah, Moataz M; Boyer, Vincent; Bongs, Kai; Holynski, Michael

2018-01-31

Recent advances in the understanding and control of quantum technologies, such as those based on cold atoms, have resulted in devices with extraordinary metrological performance. To realise this potential outside of a lab environment the size, weight and power consumption need to be reduced. Here we demonstrate the use of laser powder bed fusion, an additive manufacturing technique, as a production technique relevant to the manufacture of quantum sensors. As a demonstration we have constructed two key components using additive manufacturing, namely magnetic shielding and vacuum chambers. The initial prototypes for magnetic shields show shielding factors within a factor of 3 of conventional approaches. The vacuum demonstrator device shows that 3D-printed titanium structures are suitable for use as vacuum chambers, with the test system reaching base pressures of 5 ± 0.5 × 10 -10 mbar. These demonstrations show considerable promise for the use of additive manufacturing for cold atom based quantum technologies, in future enabling improved integrated structures, allowing for the reduction in size, weight and assembly complexity.

Maximum Expected Wall Heat Flux and Maximum Pressure After Sudden Loss of Vacuum Insulation on the Stratospheric Observatory for Infrared Astronomy (SOFIA) Liquid Helium (LHe) Dewars

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.

2014-01-01

The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared observation experiments. The experiments carry sensors cooled to liquid helium (LHe) temperatures. A question arose regarding the heat input and peak pressure that would result from a sudden loss of the dewar vacuum insulation. Owing to concerns about the adequacy of dewar pressure relief in the event of a sudden loss of the dewar vacuum insulation, the SOFIA Program engaged the NASA Engineering and Safety Center (NESC). This report summarizes and assesses the experiments that have been performed to measure the heat flux into LHe dewars following a sudden vacuum insulation failure, describes the physical limits of heat input to the dewar, and provides an NESC recommendation for the wall heat flux that should be used to assess the sudden loss of vacuum insulation case. This report also assesses the methodology used by the SOFIA Program to predict the maximum pressure that would occur following a loss of vacuum event.

Pressure sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mee, David K.; Ripley, Edward B.; Nienstedt, Zachary C.

Disclosed is a passive, in-situ pressure sensor. The sensor includes a sensing element having a ferromagnetic metal and a tension inducing mechanism coupled to the ferromagnetic metal. The tension inducing mechanism is operable to change a tensile stress upon the ferromagnetic metal based on a change in pressure in the sensing element. Changes in pressure are detected based on changes in the magnetic switching characteristics of the ferromagnetic metal when subjected to an alternating magnetic field caused by the change in the tensile stress. The sensing element is embeddable in a closed system for detecting pressure changes without the needmore » for any penetrations of the system for power or data acquisition by detecting changes in the magnetic switching characteristics of the ferromagnetic metal caused by the tensile stress.« less

Improved Thermal-Vacuum Compatible Flat Plate Radiometric Source For System-Level Testing Of Optical Sensors

NASA Technical Reports Server (NTRS)

Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.

2016-01-01

In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance.

Micro packaged MEMS pressure sensor for intracranial pressure measurement

NASA Astrophysics Data System (ADS)

Xiong, Liu; Yan, Yao; Jiahao, Ma; Yanhang, Zhang; Qian, Wang; Zhaohua, Zhang; Tianling, Ren

2015-06-01

This paper presents a micro packaged MEMS pressure sensor for intracranial pressure measurement which belongs to BioMEMS. It can be used in lumbar puncture surgery to measure intracranial pressure. Miniaturization is key for lumbar puncture surgery because the sensor must be small enough to allow it be placed in the reagent chamber of the lumbar puncture needle. The size of the sensor is decided by the size of the sensor chip and package. Our sensor chip is based on silicon piezoresistive effect and the size is 400 × 400 μm2. It is much smaller than the reported polymer intracranial pressure sensors such as liquid crystal polymer sensors. In terms of package, the traditional dual in-line package obviously could not match the size need, the minimal size of recently reported MEMS-based intracranial pressure sensors after packaging is 10 × 10 mm2. In this work, we are the first to introduce a quad flat no-lead package as the package form of piezoresistive intracranial pressure sensors, the whole size of the sensor is minimized to only 3 × 3 mm2. Considering the liquid measurement environment, the sensor is gummed and waterproof performance is tested; the sensitivity of the sensor is 0.9 × 10-2 mV/kPa. Project supported by the National Natural Science Foundation of China (Nos. 61025021, 61434001), and the ‘Thousands Talents’ Program for Pioneer Researchers and Its Innovation Team, China.

Graphene Squeeze-Film Pressure Sensors.

PubMed

Dolleman, Robin J; Davidovikj, Dejan; Cartamil-Bueno, Santiago J; van der Zant, Herre S J; Steeneken, Peter G

2016-01-13

The operating principle of squeeze-film pressure sensors is based on the pressure dependence of a membrane's resonance frequency, caused by the compression of the surrounding gas which changes the resonator stiffness. To realize such sensors, not only strong and flexible membranes are required, but also minimization of the membrane's mass is essential to maximize responsivity. Here, we demonstrate the use of a few-layer graphene membrane as a squeeze-film pressure sensor. A clear pressure dependence of the membrane's resonant frequency is observed, with a frequency shift of 4 MHz between 8 and 1000 mbar. The sensor shows a reproducible response and no hysteresis. The measured responsivity of the device is 9000 Hz/mbar, which is a factor 45 higher than state-of-the-art MEMS-based squeeze-film pressure sensors while using a 25 times smaller membrane area.

VACUUM SEALING MEANS FOR LOW VACUUM PRESSURES

DOEpatents

Milleron, N.

1962-06-12

S>A vacuum seal is designed in which the surface tension of a thin layer of liquid metal of low vapor pressure cooperates with adjacent surfaces to preclude passages of gases across pressure differentials as low as 10/sup -8/ mm Hg. Mating contiguous surfaces composed of copper, brass, stainless steel, nickel, molybdenum, tungsten, tantalum, glass, quartz, and/or synthetic mica are disposed to provide a maximum tolerance, D, expressed by 2 gamma /P/sub 1/, where gamma is the coefflcient of the surface tension of the metal sealant selected in dynes/cm/sub 2/. Means for heating the surfaces remotely is provided where temperatures drop below about 250 deg C. A sealant consisting of an alloy of gallium, indium, and tin, among other combinations tabulated, is disposed therebetween after treating the surfaces to improve wettability, as by ultrasonic vibrations, the surfaces and sealants being selected according to the anticipated experimental conditions of use. (AEC)

High pressure fiber optic sensor system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guida, Renato; Xia, Hua; Lee, Boon K

2013-11-26

The present application provides a fiber optic sensor system. The fiber optic sensor system may include a small diameter bellows, a large diameter bellows, and a fiber optic pressure sensor attached to the small diameter bellows. Contraction of the large diameter bellows under an applied pressure may cause the small diameter bellows to expand such that the fiber optic pressure sensor may measure the applied pressure.

Simplified Methodology to Estimate the Maximum Liquid Helium (LHe) Cryostat Pressure from a Vacuum Jacket Failure

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.; Richards, W. Lance

2015-01-01

The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared astronomical observation experiments. These experiments carry sensors cooled to liquid helium temperatures. The liquid helium supply is contained in large (i.e., 10 liters or more) vacuum-insulated dewars. Should the dewar vacuum insulation fail, the inrushing air will condense and freeze on the dewar wall, resulting in a large heat flux on the dewar's contents. The heat flux results in a rise in pressure and the actuation of the dewar pressure relief system. A previous NASA Engineering and Safety Center (NESC) assessment provided recommendations for the wall heat flux that would be expected from a loss of vacuum and detailed an appropriate method to use in calculating the maximum pressure that would occur in a loss of vacuum event. This method involved building a detailed supercritical helium compressible flow thermal/fluid model of the vent stack and exercising the model over the appropriate range of parameters. The experimenters designing science instruments for SOFIA are not experts in compressible supercritical flows and do not generally have access to the thermal/fluid modeling packages that are required to build detailed models of the vent stacks. Therefore, the SOFIA Program engaged the NESC to develop a simplified methodology to estimate the maximum pressure in a liquid helium dewar after the loss of vacuum insulation. The method would allow the university-based science instrument development teams to conservatively determine the cryostat's vent neck sizing during preliminary design of new SOFIA Science Instruments. This report details the development of the simplified method, the method itself, and the limits of its applicability. The simplified methodology provides an estimate of the dewar pressure after a loss of vacuum insulation that can be used for the initial design of the liquid helium dewar vent stacks. However, since it is not an exact

Electronically-Scanned Pressure Sensors

NASA Technical Reports Server (NTRS)

Coe, C. F.; Parra, G. T.; Kauffman, R. C.

1984-01-01

Sensors not pneumatically switched. Electronic pressure-transducer scanning system constructed in modular form. Pressure transducer modules and analog to digital converter module small enough to fit within cavities of average-sized wind-tunnel models. All switching done electronically. Temperature controlled environment maintained within sensor modules so accuracy maintained while ambient temperature varies.

Transmission geometry laserspray ionization vacuum using an atmospheric pressure inlet.

PubMed

Lutomski, Corinne A; El-Baba, Tarick J; Inutan, Ellen D; Manly, Cory D; Wager-Miller, James; Mackie, Ken; Trimpin, Sarah

2014-07-01

This represents the first report of laserspray ionization vacuum (LSIV) with operation directly from atmospheric pressure for use in mass spectrometry. Two different types of electrospray ionization source inlets were converted to LSIV sources by equipping the entrance of the atmospheric pressure inlet aperture with a customized cone that is sealed with a removable glass plate holding the matrix/analyte sample. A laser aligned in transmission geometry (at 180° relative to the inlet) ablates the matrix/analyte sample deposited on the vacuum side of the glass slide. Laser ablation from vacuum requires lower inlet temperature relative to laser ablation at atmospheric pressure. However, higher inlet temperature is required for high-mass analytes, for example, α-chymotrypsinogen (25.6 kDa). Labile compounds such as gangliosides and cardiolipins are detected in the negative ion mode directly from mouse brain tissue as intact doubly deprotonated ions. Multiple charging enhances the ion mobility spectrometry separation of ions derived from complex tissue samples.

Transmission Geometry Laserspray Ionization Vacuum Using an Atmospheric Pressure Inlet

PubMed Central

2015-01-01

This represents the first report of laserspray ionization vacuum (LSIV) with operation directly from atmospheric pressure for use in mass spectrometry. Two different types of electrospray ionization source inlets were converted to LSIV sources by equipping the entrance of the atmospheric pressure inlet aperture with a customized cone that is sealed with a removable glass plate holding the matrix/analyte sample. A laser aligned in transmission geometry (at 180° relative to the inlet) ablates the matrix/analyte sample deposited on the vacuum side of the glass slide. Laser ablation from vacuum requires lower inlet temperature relative to laser ablation at atmospheric pressure. However, higher inlet temperature is required for high-mass analytes, for example, α-chymotrypsinogen (25.6 kDa). Labile compounds such as gangliosides and cardiolipins are detected in the negative ion mode directly from mouse brain tissue as intact doubly deprotonated ions. Multiple charging enhances the ion mobility spectrometry separation of ions derived from complex tissue samples. PMID:24896880

HOPG/ZnO/HOPG pressure sensor

NASA Astrophysics Data System (ADS)

Jahangiri, Mojtaba; Yousefiazari, Ehsan; Ghalamboran, Milad

2017-12-01

Pressure sensor is one of the most commonly used sensors in the research laboratories and industries. These are generally categorized in three different classes of absolute pressure sensors, gauge pressure sensors, and differential pressure sensors. In this paper, we fabricate and assess the pressure sensitivity of the current vs. voltage diagrams in a graphite/ZnO/graphite structure. Zinc oxide layers are deposited on highly oriented pyrolytic graphite (HOPG) substrates by sputtering a zinc target under oxygen plasma. The top electrode is also a slice of HOPG which is placed on the ZnO layer and connected to the outside electronic circuits. By recording the I-V characteristics of the device under different forces applied to the top HOPG electrode, the pressure sensitivity is demonstrated; at the optimum biasing voltage, the device current changes 10 times upon changing the pressure level on the top electrode by 20 times. Repeatability and reproducibility of the observed effect is studied on the same and different samples. All the materials used for the fabrication of this pressure sensor are biocompatible, the fabricated device is anticipated to find potential applications in biomedical engineering.

Fixture For Mounting A Pressure Sensor

NASA Technical Reports Server (NTRS)

Cagle, Christopher M.

1995-01-01

Fixture for mounting pressure sensor in aerodynamic model simplifies task of removal and replacement of sensor in event sensor becomes damaged. Makes it unnecessary to dismantle model. Also minimizes any change in aerodynamic characteristics of model in event of replacement. Removable pressure sensor installed in fixture in wall of model. Wires from sensor pass through channel under surface.

33 CFR 159.111 - Pressure and vacuum pulse test.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Pressure and vacuum pulse test. 159.111 Section 159.111 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) POLLUTION MARINE SANITATION DEVICES Design, Construction, and Testing § 159.111 Pressure and...

Fiber Bragg grating sensors for real-time monitoring of evacuation process

NASA Astrophysics Data System (ADS)

Guru Prasad, A. S.; Hegde, Gopalkrishna M.; Asokan, S.

2010-03-01

Fiber bragg grating (FBG) sensors have been widely used for number of sensing applications like temperature, pressure, acousto-ultrasonic, static and dynamic strain, refractive index change measurements and so on. Present work demonstrates the use of FBG sensors in in-situ measurement of vacuum process with simultaneous leak detection capability. Experiments were conducted in a bell jar vacuum chamber facilitated with conventional Pirani gauge for vacuum measurement. Three different experiments have been conducted to validate the performance of FBG sensor in monitoring vacuum creating process and air bleeding. The preliminary results of FBG sensors in vacuum monitoring have been compared with that of commercial Pirani gauge sensor. This novel technique offers a simple alternative to conventional method for real time monitoring of evacuation process. Proposed FBG based vacuum sensor has potential applications in vacuum systems involving hazardous environment such as chemical and gas plants, automobile industries, aeronautical establishments and leak monitoring in process industries, where the electrical or MEMS based sensors are prone to explosion and corrosion.

Alpha-Particle Gas-Pressure Sensor

NASA Technical Reports Server (NTRS)

Buehler, M. C.; Bell, L. D.; Hecht, M. H.

1996-01-01

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

Carbon nanotube temperature and pressure sensors

DOEpatents

Ivanov, Ilia N.; Geohegan, David B.

2016-11-15

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Carbon nanotube temperature and pressure sensors

DOEpatents

Ivanov, Ilia N.; Geohegan, David B.

2016-12-13

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Carbon nanotube temperature and pressure sensors

DOEpatents

Ivanov, Ilia N; Geohegan, David Bruce

2013-10-29

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Carbon nanotube temperature and pressure sensors

DOEpatents

Ivanov, Ilia N.; Geohegan, David B.

2016-10-25

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

Carbon nanotube temperature and pressure sensors

DOEpatents

Ivanov, Ilia N.; Geohegan, David B.

2017-09-12

The present invention, in one embodiment, provides a method of measuring pressure or temperature using a sensor including a sensor element composed of a plurality of carbon nanotubes. In one example, the resistance of the plurality of carbon nanotubes is measured in response to the application of temperature or pressure. The changes in resistance are then recorded and correlated to temperature or pressure. In one embodiment, the present invention provides for independent measurement of pressure or temperature using the sensors disclosed herein.

A temperature and pressure controlled calibration system for pressure sensors

NASA Technical Reports Server (NTRS)

Chapman, John J.; Kahng, Seun K.

1989-01-01

A data acquisition and experiment control system capable of simulating temperatures from -184 to +220 C and pressures either absolute or differential from 0 to 344.74 kPa is developed to characterize silicon pressure sensor response to temperature and pressure. System software is described that includes sensor data acquisition, algorithms for numerically derived thermal offset and sensitivity correction, and operation of the environmental chamber and pressure standard. This system is shown to be capable of computer interfaced cryogenic testing to within 1 C and 34.47 Pa of single channel or multiplexed arrays of silicon pressure sensors.

Non-reclosing pressure relief device for vacuum systems

DOEpatents

Swansiger, William A.

1994-01-01

A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife.

Non-reclosing pressure relief device for vacuum systems

DOEpatents

Swansiger, W.A.

1994-02-08

A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife. 6 figures.

Extension of the shelf life of prawns (Penaeus japonicus) by vacuum packaging and high-pressure treatment.

PubMed

López-Caballero, M E; Pérez-Mateos, M; Borderías, J A; Montero, P

2000-10-01

The present study has investigated the application of high pressures (200 and 400 MPa) in chilled prawn tails, both conventionally stored (air) and vacuum packaged. Vacuum packaging and high-pressure treatment did extend the shelf life of the prawn samples, although it did affect muscle color very slightly, giving it a whiter appearance. The viable shelf life of 1 week for the air-stored samples was extended to 21 days in the vacuum-packed samples, 28 days in the samples treated at 200 MPa, and 35 days in the samples pressurized at 400 MPa. Vacuum packaging checked the onset of blackening, whereas high-pressure treatment aggravated the problem. From a microbiological point of view, batches conventionally stored reached about 6 log CFU/g or even higher at 14 days. Similar figures were reached in total number of bacteria in vacuum-packed samples and in pressurized at 200-MPa samples at 21 days. When samples were pressurized at 400 MPa, total numbers of bacteria were below 5.5 log CFU/g at 35 days of storage. Consequently, a combination of vacuum packaging and high-pressure treatment would appear to be beneficial in prolonging freshness and preventing spotting.

Multi-parameter fibre Bragg grating sensor-array for thermal vacuum cycling test

NASA Astrophysics Data System (ADS)

Cheng, L.; Ahlers, B.; Toet, P.; Casarosa, G.; Appolloni, M.

2017-11-01

Fibre Bragg Grating (FBG) sensor systems based on optical fibres are gaining interest in space applications. Studies on Structural Health Monitoring (SHM) of the reusable launchers using FBG sensors have been carried out in the Future European Space Transportation Investigations Programme (FESTIP). Increasing investment in the development on FBG sensor applications is foreseen for the Future Launchers Preparatory Programme (FLPP). TNO has performed different SHM measurements with FBGs including on the VEGA interstage [1, 2] in 2006. Within the current project, a multi-parameter FBG sensor array demonstrator system for temperature and strain measurements is designed, fabricated and tested under ambient as well as Thermal Vacuum (TV) conditions in a TV chamber of the European Space Agency (ESA), ESTEC site. The aim is the development of a multi-parameters measuring system based on FBG technology for space applications. During the TV tests of a Space Craft (S/C) or its subsystems, thermal measurements, as well as strain measurements are needed by the engineers in order to verify their prediction and to validate their models. Because of the dimensions of the test specimen and the accuracy requested to the measurement, a large number of observation/measuring points are needed. Conventional sensor systems require a complex routing of the cables connecting the sensors to their acquisition unit. This will add extra weight to the construction under test. FBG sensors are potentially light-weight and can easily be multiplexed in an array configuration. The different tasks comply of a demonstrator system design; its component selection, procurement, manufacturing and finally its assembly. The temperature FBG sensor is calibrated in a dedicated laboratory setup down to liquid nitrogen (LN2) temperature at TNO. A temperature-wavelength calibration curve is generated. After a test programme definition a setup in thermal vacuum is realised at ESA premises including a mechanical

Distributed pressure sensors for a urethral catheter.

PubMed

Ahmadi, Mahdi; Rajamani, Rajesh; Timm, Gerald; Sezen, A S

2015-01-01

A flexible strip that incorporates multiple pressure sensors and is capable of being fixed to a urethral catheter is developed. The urethral catheter thus instrumented will be useful for measurement of pressure in a human urethra during urodynamic testing in a clinic. This would help diagnose the causes of urinary incontinence in patients. Capacitive pressure sensors are fabricated on a flexible polyimide-copper substrate using surface micromachining processes and alignment/assembly of the top and bottom portions of the sensor strip. The developed sensor strip is experimentally evaluated in an in vitro test rig using a pressure chamber. The sensor strip is shown to have adequate sensitivity and repeatability. While the calibration factors for the sensors on the strip vary from one sensor to another, even the least sensitive sensor has a resolution better than 0.1 psi.

Applications of pressure-sensitive dielectric elastomer sensors

NASA Astrophysics Data System (ADS)

Böse, Holger; Ocak, Deniz; Ehrlich, Johannes

2016-04-01

Dielectric elastomer sensors for the measurement of compression loads with high sensitivity are described. The basic design of the sensors exhibits two profiled surfaces between which an elastomer film is confined. All components of the sensor were prepared with silicone whose stiffness can be varied in a wide range. Depending on details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression and electrode layers on the elastomer profiles and in the elastomer film approach each other. Different designs of the pressure sensor give rise to very different sensor characteristics in terms of the dependence of electric capacitance on compression force. Due to their inherent flexibility, the pressure sensors can be used on compliant substrates such as seats or beds or on the human body. This gives rise to numerous possible applications. The contribution describes also some examples of possible sensor applications. A glove was equipped with various sensors positioned at the finger tips. When grabbing an object with the glove, the sensors can detect the gripping forces of the individual fingers with high sensitivity. In a demonstrator of the glove equipped with seven sensors, the capacitances representing the gripping forces are recorded on a display. In another application example, a lower limb prosthesis was equipped with a pressure sensor to detect the load on the remaining part of the leg and the load is displayed in terms of the measured capacitance. The benefit of such sensors is to detect an eventual overload in order to prevent possible pressure sores. A third example introduces a seat load sensor system based on four extended pressure sensor mats. The sensor system detects the load distribution of a person on the seat. The examples emphasize the high performance of the new pressure sensor technology.

Low temperature ablation models made by pressure/vacuum application

NASA Technical Reports Server (NTRS)

Fischer, M. C.; Heier, W. C.

1970-01-01

Method developed employs high pressure combined with strong vacuum force to compact ablation models into desired conical shape. Technique eliminates vapor hazard and results in high material density providing excellent structural integrity.

A transparent bending-insensitive pressure sensor

NASA Astrophysics Data System (ADS)

Lee, Sungwon; Reuveny, Amir; Reeder, Jonathan; Lee, Sunghoon; Jin, Hanbit; Liu, Qihan; Yokota, Tomoyuki; Sekitani, Tsuyoshi; Isoyama, Takashi; Abe, Yusuke; Suo, Zhigang; Someya, Takao

2016-05-01

Measuring small normal pressures is essential to accurately evaluate external stimuli in curvilinear and dynamic surfaces such as natural tissues. Usually, sensitive and spatially accurate pressure sensors are achieved through conformal contact with the surface; however, this also makes them sensitive to mechanical deformation (bending). Indeed, when a soft object is pressed by another soft object, the normal pressure cannot be measured independently from the mechanical stress. Here, we show a pressure sensor that measures only the normal pressure, even under extreme bending conditions. To reduce the bending sensitivity, we use composite nanofibres of carbon nanotubes and graphene. Our simulations show that these fibres change their relative alignment to accommodate bending deformation, thus reducing the strain in individual fibres. Pressure sensitivity is maintained down to a bending radius of 80 μm. To test the suitability of our sensor for soft robotics and medical applications, we fabricated an integrated sensor matrix that is only 2 μm thick. We show real-time (response time of ∼20 ms), large-area, normal pressure monitoring under different, complex bending conditions.

Safety shield for vacuum/pressure chamber viewing port

NASA Technical Reports Server (NTRS)

Shimansky, R. A.; Spencer, R. S. (Inventor)

1981-01-01

Observers are protected from flying debris resulting from a failure of a vacuum or pressure chamber viewing port following an implosion or explosion by an optically clear shatter resistant safety shield which spaced apart from the viewing port on the outer surface of the chamber.

49 CFR 195.264 - Impoundment, protection against entry, normal/emergency venting or pressure/vacuum relief for...

Code of Federal Regulations, 2010 CFR

2010-10-01

... devices must be provided for each low-pressure and high-pressure breakout tank. (e) For normal/emergency... and vacuum-relieving devices installed on high pressure tanks built to API Standard 2510 (incorporated.../emergency venting or pressure/vacuum relief for aboveground breakout tanks. 195.264 Section 195.264...

Introduction to total- and partial-pressure measurements in vacuum systems

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Kern, F. A.

1989-01-01

An introduction to the fundamentals of total and partial pressure measurement in the vacuum regime (760 x 10 to the -16th power Torr) is presented. The instrument most often used in scientific fields requiring vacuum measurement are discussed with special emphasis on ionization type gauges and quadrupole mass spectrometers. Some attention is also given to potential errors in measurement as well as calibration techniques.

Fluctuation of a Piston in Vacuum Induced by Thermal Radiation Pressure

NASA Astrophysics Data System (ADS)

Inui, Norio

2017-10-01

We consider the displacement of a piston dividing a vacuum cavity at a finite temperature T induced by fluctuations in the thermal radiation pressure. The correlation function of the thermal radiation pressure is calculated using the theoretical framework developed by Barton, which was first applied to the fluctuation of the Casimir force at absolute zero. We show that the variance of the radiation pressure at a fixed point is proportional to T8 and evaluate the mean square displacement for a piston with a small cross section in a characteristic correlation timescale ħ/(kBT). At room temperature, the contribution of the thermal radiation to the fluctuation is larger than that of the vacuum fluctuation.

The digital compensation technology system for automotive pressure sensor

NASA Astrophysics Data System (ADS)

Guo, Bin; Li, Quanling; Lu, Yi; Luo, Zai

2011-05-01

Piezoresistive pressure sensor be made of semiconductor silicon based on Piezoresistive phenomenon, has many characteristics. But since the temperature effect of semiconductor, the performance of silicon sensor is also changed by temperature, and the pressure sensor without temperature drift can not be produced at present. This paper briefly describe the principles of sensors, the function of pressure sensor and the various types of compensation method, design the detailed digital compensation program for automotive pressure sensor. Simulation-Digital mixed signal conditioning is used in this dissertation, adopt signal conditioning chip MAX1452. AVR singlechip ATMEGA128 and other apparatus; fulfill the design of digital pressure sensor hardware circuit and singlechip hardware circuit; simultaneously design the singlechip software; Digital pressure sensor hardware circuit is used to implementing the correction and compensation of sensor; singlechip hardware circuit is used to implementing to controll the correction and compensation of pressure sensor; singlechip software is used to implementing to fulfill compensation arithmetic. In the end, it implement to measure the output of sensor, and contrast to the data of non-compensation, the outcome indicates that the compensation precision of compensated sensor output is obviously better than non-compensation sensor, not only improving the compensation precision but also increasing the stabilization of pressure sensor.

Acceleration sensitivity of micromachined pressure sensors

NASA Astrophysics Data System (ADS)

August, Richard; Maudie, Theresa; Miller, Todd F.; Thompson, Erik

1999-08-01

Pressure sensors serve a variety of automotive applications, some which may experience high levels of acceleration such as tire pressure monitoring. To design pressure sensors for high acceleration environments it is important to understand their sensitivity to acceleration especially if thick encapsulation layers are used to isolate the device from the hostile environment in which they reside. This paper describes a modeling approach to determine their sensitivity to acceleration that is very general and is applicable to different device designs and configurations. It also describes the results of device testing of a capacitive surface micromachined pressure sensor at constant acceleration levels from 500 to 2000 g's.

High Temperature Dynamic Pressure Measurements Using Silicon Carbide Pressure Sensors

NASA Technical Reports Server (NTRS)

Okojie, Robert S.; Meredith, Roger D.; Chang, Clarence T.; Savrun, Ender

2014-01-01

Un-cooled, MEMS-based silicon carbide (SiC) static pressure sensors were used for the first time to measure pressure perturbations at temperatures as high as 600 C during laboratory characterization, and subsequently evaluated in a combustor rig operated under various engine conditions to extract the frequencies that are associated with thermoacoustic instabilities. One SiC sensor was placed directly in the flow stream of the combustor rig while a benchmark commercial water-cooled piezoceramic dynamic pressure transducer was co-located axially but kept some distance away from the hot flow stream. In the combustor rig test, the SiC sensor detected thermoacoustic instabilities across a range of engine operating conditions, amplitude magnitude as low as 0.5 psi at 585 C, in good agreement with the benchmark piezoceramic sensor. The SiC sensor experienced low signal to noise ratio at higher temperature, primarily due to the fact that it was a static sensor with low sensitivity.

A silicon micromachined resonant pressure sensor

NASA Astrophysics Data System (ADS)

Tang, Zhangyang; Fan, Shangchun; Cai, Chenguang

2009-09-01

This paper describes the design, fabrication and test of a silicon micromachined resonant pressure sensor. A square membrane and a doubly clamped resonant beam constitute a compound structure. The former senses the pressure directly, while the latter changes its resonant frequency according to deformation of the membrane. The final output relation between the resonant frequency and the applied pressure is deducted according to the structure mechanical properties. Sensors are fabricated by micromachining technology, and then sealed in vaccum. These sensors are tested by open-loop and close-loop system designed on purpose. The experiment results demonstrate that the sensor has a sensitivity of 49.8Hz/kPa and repeatability of 0.08%.

Flight testing of a luminescent surface pressure sensor

NASA Technical Reports Server (NTRS)

Mclachlan, B. G.; Bell, J. H.; Espina, J.; Gallery, J.; Gouterman, M.; Demandante, C. G. N.; Bjarke, L.

1992-01-01

NASA ARC has conducted flight tests of a new type of aerodynamic pressure sensor based on a luminescent surface coating. Flights were conducted at the NASA ARC-Dryden Flight Research Facility. The luminescent pressure sensor is based on a surface coating which, when illuminated with ultraviolet light, emits visible light with an intensity dependent on the local air pressure on the surface. This technique makes it possible to obtain pressure data over the entire surface of an aircraft, as opposed to conventional instrumentation, which can only make measurements at pre-selected points. The objective of the flight tests was to evaluate the effectiveness and practicality of a luminescent pressure sensor in the actual flight environment. A luminescent pressure sensor was installed on a fin, the Flight Test Fixture (FTF), that is attached to the underside of an F-104 aircraft. The response of one particular surface coating was evaluated at low supersonic Mach numbers (M = 1.0-1.6) in order to provide an initial estimate of the sensor's capabilities. This memo describes the test approach, the techniques used, and the pressure sensor's behavior under flight conditions. A direct comparison between data provided by the luminescent pressure sensor and that produced by conventional pressure instrumentation shows that the luminescent sensor can provide quantitative data under flight conditions. However, the test results also show that the sensor has a number of limitations which must be addressed if this technique is to prove useful in the flight environment.

Pressure Measurement Sensor

NASA Technical Reports Server (NTRS)

1997-01-01

FFPI Industries Inc. is the manufacturer of fiber-optic sensors that furnish accurate pressure measurements in internal combustion chambers. Such an assessment can help reduce pollution emitted by these engines. A chief component in the sensor owes its seven year- long development to Lewis Research Center funding to embed optical fibers and sensors in metal parts. NASA support to Texas A&M University played a critical role in developing this fiber optic technology and led to the formation of FFPI Industries and the production of fiber sensor products. The simple, rugged design of the sensor offers the potential for mass production at low cost. Widespread application of the new technology is forseen, from natural gas transmission, oil refining and electrical power generation to rail transport and the petrochemical paper product industry.

Self-correcting electronically scanned pressure sensor

NASA Technical Reports Server (NTRS)

Gross, C. (Inventor)

1983-01-01

A multiple channel high data rate pressure sensing device is disclosed for use in wind tunnels, spacecraft, airborne, process control, automotive, etc., pressure measurements. Data rates in excess of 100,000 measurements per second are offered with inaccuracies from temperature shifts less than 0.25% (nominal) of full scale over a temperature span of 55 C. The device consists of thirty-two solid state sensors, signal multiplexing electronics to electronically address each sensor, and digital electronic circuitry to automatically correct the inherent thermal shift errors of the pressure sensors and their associated electronics.

High-temperature fiber optic pressure sensor

NASA Technical Reports Server (NTRS)

Berthold, J. W.

1984-01-01

Attention is given to a program to develop fiber optic methods to measure diaphragm deflection. The end application is intended for pressure transducers capable of operating to 540 C. In this paper are reported the results of a laboratory study to characterize the performance of the fiber-optic microbend sensor. The data presented include sensitivity and spring constant. The advantages and limitations of the microbend sensor for static pressure measurement applications are described. A proposed design is presented for a 540 C pressure transducer using the fiber optic microbend sensor.

A vacuum gauge based on an ultracold gas

NASA Astrophysics Data System (ADS)

Makhalov, V. B.; Turlapov, A. V.

2017-06-01

We report the design and application of a primary vacuum gauge based on an ultracold gas of atoms in an optical dipole trap. The pressure is calculated from the confinement time for atoms in the trap. The relationship between pressure and confinement time is established from the first principles owing to elimination of all channels introducing losses, except for knocking out an atom from the trap due to collisions with a residual gas particle. The method requires the knowledge of the gas chemical composition in the vacuum chamber, and, in the absence of this information, the systematic error is less than that of the ionisation sensor.

Pressure sensor to determine spatial pressure distributions on boundary layer flows

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Piroozan, Parham; Corke, Thomas C.

1997-03-01

The determination of pressures along the surface of a wind tunnel proves difficult with methods that must introduce devices into the flow stream. This paper presents a sensor that is part of the wall. A special interferometric reflection moire technique is developed and used to produce signals that measures pressure both in static and dynamic settings. The sensor developed is an intelligent sensor that combines optics and electronics to analyze the pressure patterns. The sensor provides the input to a control system that is capable of modifying the shape of the wall and preserve the stability of the flow.

Method and Apparatus for Characterizing Pressure Sensors using Modulated Light Beam Pressure

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor)

2003-01-01

Embodiments of apparatuses and methods are provided that use light sources instead of sound sources for characterizing and calibrating sensors for measuring small pressures to mitigate many of the problems with using sound sources. In one embodiment an apparatus has a light source for directing a beam of light on a sensing surface of a pressure sensor for exerting a force on the sensing surface. The pressure sensor generates an electrical signal indicative of the force exerted on the sensing surface. A modulator modulates the beam of light. A signal processor is electrically coupled to the pressure sensor for receiving the electrical signal.

Microfabricated pressure and shear stress sensors

NASA Technical Reports Server (NTRS)

Liu, Chang (Inventor); Chen, Jack (Inventor); Engel, Jonathan (Inventor)

2009-01-01

A microfabricated pressure sensor. The pressure sensor comprises a raised diaphragm disposed on a substrate. The diaphragm is configured to bend in response to an applied pressure difference. A strain gauge of a conductive material is coupled to a surface of the raised diaphragm and to at least one of the substrate and a piece rigidly connected to the substrate.

Novel designs for application specific MEMS pressure sensors.

PubMed

Fragiacomo, Giulio; Reck, Kasper; Lorenzen, Lasse; Thomsen, Erik V

2010-01-01

In the framework of developing innovative microfabricated pressure sensors, we present here three designs based on different readout principles, each one tailored for a specific application. A touch mode capacitive pressure sensor with high sensitivity (14 pF/bar), low temperature dependence and high capacitive output signal (more than 100 pF) is depicted. An optical pressure sensor intrinsically immune to electromagnetic interference, with large pressure range (0-350 bar) and a sensitivity of 1 pm/bar is presented. Finally, a resonating wireless pressure sensor power source free with a sensitivity of 650 KHz/mmHg is described. These sensors will be related with their applications in harsh environment, distributed systems and medical environment, respectively. For many aspects, commercially available sensors, which in vast majority are piezoresistive, are not suited for the applications proposed.

Passive blast pressure sensor

DOEpatents

King, Michael J.; Sanchez, Roberto J.; Moss, William C.

2013-03-19

A passive blast pressure sensor for detecting blast overpressures of at least a predetermined minimum threshold pressure. The blast pressure sensor includes a piston-cylinder arrangement with one end of the piston having a detection surface exposed to a blast event monitored medium through one end of the cylinder and the other end of the piston having a striker surface positioned to impact a contact stress sensitive film that is positioned against a strike surface of a rigid body, such as a backing plate. The contact stress sensitive film is of a type which changes color in response to at least a predetermined minimum contact stress which is defined as a product of the predetermined minimum threshold pressure and an amplification factor of the piston. In this manner, a color change in the film arising from impact of the piston accelerated by a blast event provides visual indication that a blast overpressure encountered from the blast event was not less than the predetermined minimum threshold pressure.

Urodynamic pressure sensor

NASA Technical Reports Server (NTRS)

Moore, Thomas

1991-01-01

A transducer system was developed for measuring the closing pressure profile along the female urethra, which provides up to five sensors within the functional length of the urethra. This new development is an improvement over an earlier measurement method that has a smaller sensor area and was unable to respond to transient events. Three sensors were constructed; one of them was subjected to approximately eight hours of use in a clinical setting during which 576 data points were obtained. The complete instrument system, including the signal conditioning electronics, data acquisition unit, and the computer with its display and printer is described and illustrated.

Flexible Sensors for Pressure Therapy: Effect of Substrate Curvature and Stiffness on Sensor Performance.

PubMed

Khodasevych, Iryna; Parmar, Suresh; Troynikov, Olga

2017-10-20

Flexible pressure sensors are increasingly being used in medical and non-medical applications, and particularly in innovative health monitoring. Their efficacy in medical applications such as compression therapy depends on the accuracy and repeatability of their output, which in turn depend on factors such as sensor type, shape, pressure range, and conformability of the sensor to the body surface. Numerous researchers have examined the effects of sensor type and shape, but little information is available on the effect of human body parameters such as support surfaces' curvature and the stiffness of soft tissues on pressure sensing performance. We investigated the effects of body parameters on the performance of pressure sensors using a custom-made human-leg-like test setup. Pressure sensing parameters such as accuracy, drift and repeatability were determined in both static (eight hours continuous pressure) and dynamic (10 cycles of pressure application of 30 s duration) testing conditions. The testing was performed with a focus on compression therapy application for venous leg ulcer treatments, and was conducted in a low-pressure range of 20-70 mmHg. Commercially available sensors manufactured by Peratech and Sensitronics were used under various loading conditions to determine the influence of stiffness and curvature. Flat rigid, flat soft silicone and three cylindrical silicone surfaces of radii of curvature of 3.5 cm, 5.5 cm and 6.5 cm were used as substrates under the sensors. The Peratech sensor averaged 94% accuracy for both static and dynamic measurements on all substrates; the Sensitronics sensor averaged 88% accuracy. The Peratech sensor displayed moderate variations and the Sensitronics sensor large variations in output pressure readings depending on the underlying test surface, both of which were reduced markedly by individual pressure calibration for surface type. Sensor choice and need for calibration to surface type are important considerations for

Flexible Sensors for Pressure Therapy: Effect of Substrate Curvature and Stiffness on Sensor Performance

PubMed Central

Khodasevych, Iryna; Parmar, Suresh

2017-01-01

Flexible pressure sensors are increasingly being used in medical and non-medical applications, and particularly in innovative health monitoring. Their efficacy in medical applications such as compression therapy depends on the accuracy and repeatability of their output, which in turn depend on factors such as sensor type, shape, pressure range, and conformability of the sensor to the body surface. Numerous researchers have examined the effects of sensor type and shape, but little information is available on the effect of human body parameters such as support surfaces’ curvature and the stiffness of soft tissues on pressure sensing performance. We investigated the effects of body parameters on the performance of pressure sensors using a custom-made human-leg-like test setup. Pressure sensing parameters such as accuracy, drift and repeatability were determined in both static (eight hours continuous pressure) and dynamic (10 cycles of pressure application of 30 s duration) testing conditions. The testing was performed with a focus on compression therapy application for venous leg ulcer treatments, and was conducted in a low-pressure range of 20–70 mmHg. Commercially available sensors manufactured by Peratech and Sensitronics were used under various loading conditions to determine the influence of stiffness and curvature. Flat rigid, flat soft silicone and three cylindrical silicone surfaces of radii of curvature of 3.5 cm, 5.5 cm and 6.5 cm were used as substrates under the sensors. The Peratech sensor averaged 94% accuracy for both static and dynamic measurements on all substrates; the Sensitronics sensor averaged 88% accuracy. The Peratech sensor displayed moderate variations and the Sensitronics sensor large variations in output pressure readings depending on the underlying test surface, both of which were reduced markedly by individual pressure calibration for surface type. Sensor choice and need for calibration to surface type are important considerations for

Thermocouples of tantalum and rhenium alloys for more stable vacuum-high temperature performance

NASA Technical Reports Server (NTRS)

Morris, J. F. (Inventor)

1977-01-01

Thermocouples of the present invention provide stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor wherein each metal of the sensor is selected from a group of metals comprising tantalum and rhenium and alloys containing only those two metals. The tantalum, rhenium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibilities and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys of the present invention result in improved emf, temperature properties and thermocouple hot junction performance. The thermocouples formed of the tantalum, rhenium alloys exhibit reliability and performance stability in systems involving high temperatures and vacuums and are adaptable to space propulsion and power systems and nuclear environments.

Pressure sensor for sealed containers

DOEpatents

Hodges, Franklin R.

2001-01-01

A magnetic pressure sensor for sensing a pressure change inside a sealed container. The sensor includes a sealed deformable vessel having a first end attachable to an interior surface of the sealed container, and a second end. A magnet mounted to the vessel second end defining a distance away from the container surface provides an externally detectable magnetic field. A pressure change inside the sealed container causes deformation of the vessel changing the distance of the magnet away from the container surface, and thus the detectable intensity of the magnetic field.

Microoptomechanical sensor for intracranial pressure monitoring

NASA Astrophysics Data System (ADS)

Andreeva, A. V.; Luchinin, V. V.; Lutetskiy, N. A.; Sergushichev, A. N.

2014-12-01

The main idea of this research is the development of microoptomechanical sensor for intracranial pressure monitoring. Currently, the authors studied the scientific and technical knowledge in this field, as well as develop and test a prototype of microoptomechanical sensor for intracranial pressure (ICP) monitoring.

Bio-Inspired Stretchable Absolute Pressure Sensor Network

PubMed Central

Guo, Yue; Li, Yu-Hung; Guo, Zhiqiang; Kim, Kyunglok; Chang, Fu-Kuo; Wang, Shan X.

2016-01-01

A bio-inspired absolute pressure sensor network has been developed. Absolute pressure sensors, distributed on multiple silicon islands, are connected as a network by stretchable polyimide wires. This sensor network, made on a 4’’ wafer, has 77 nodes and can be mounted on various curved surfaces to cover an area up to 0.64 m × 0.64 m, which is 100 times larger than its original size. Due to Micro Electro-Mechanical system (MEMS) surface micromachining technology, ultrathin sensing nodes can be realized with thicknesses of less than 100 µm. Additionally, good linearity and high sensitivity (~14 mV/V/bar) have been achieved. Since the MEMS sensor process has also been well integrated with a flexible polymer substrate process, the entire sensor network can be fabricated in a time-efficient and cost-effective manner. Moreover, an accurate pressure contour can be obtained from the sensor network. Therefore, this absolute pressure sensor network holds significant promise for smart vehicle applications, especially for unmanned aerial vehicles. PMID:26729134

Phase-sensitive techniques applied to a micromachined vacuum sensor

NASA Astrophysics Data System (ADS)

Chapman, Glenn H.; Sawadsky, N.; Juneja, P. P.

1996-09-01

Phase sensitive AC measurement techniques are particularly applicable to micromachined sensors detecting temperature changes at a sensor caused by a microheater. The small mass produces rapid thermal response to AC signals which are easily detectable with lock-in amplifiers. Phase sensitive measurements were applied to a CMOS compatible micromachined pressure sensor consisting a polysilicon sense line, 760 microns long, on an oxide microbridge separated by 6 microns on each horizontal side from similar polysilicon heaters, all over a micromachined cavity. Sinusoidal heater signals at 32 Hz induced temperature caused sense line resistance changes at 64 Hz. The lock-in detected this as a first harmonic sense resistor voltage from a DC constant sense current. By observing the first harmonic the lock-in rejects all AC coupling of noise by capacitance or inductance, by measuring only those signals at the 64 Hz frequency and with a fixed phase relationship to the heater driver signals. This sensor produces large signals near atmospheric pressure, declining to 7 (mu) V below 0.1 mTorr. Phase measurements between 760 and 100 Torr where the air's thermal conductivity changes little, combined with amplitude changes at low pressure generate a pressure measurement accurate at 5 percent from 760 Torr to 10 mTorr, sensing of induced temperature changes of 0.001 degree C.

Novel Designs for Application Specific MEMS Pressure Sensors

PubMed Central

Fragiacomo, Giulio; Reck, Kasper; Lorenzen, Lasse; Thomsen, Erik V.

2010-01-01

In the framework of developing innovative microfabricated pressure sensors, we present here three designs based on different readout principles, each one tailored for a specific application. A touch mode capacitive pressure sensor with high sensitivity (14 pF/bar), low temperature dependence and high capacitive output signal (more than 100 pF) is depicted. An optical pressure sensor intrinsically immune to electromagnetic interference, with large pressure range (0–350 bar) and a sensitivity of 1 pm/bar is presented. Finally, a resonating wireless pressure sensor power source free with a sensitivity of 650 KHz/mmHg is described. These sensors will be related with their applications in harsh environment, distributed systems and medical environment, respectively. For many aspects, commercially available sensors, which in vast majority are piezoresistive, are not suited for the applications proposed. PMID:22163425

The baseline pressure of intracranial pressure (ICP) sensors can be altered by electrostatic discharges.

PubMed

Eide, Per K; Bakken, André

2011-08-22

The monitoring of intracranial pressure (ICP) has a crucial role in the surveillance of patients with brain injury. During long-term monitoring of ICP, we have seen spontaneous shifts in baseline pressure (ICP sensor zero point), which are of technical and not physiological origin. The aim of the present study was to explore whether or not baseline pressures of ICP sensors can be affected by electrostatics discharges (ESD's), when ESD's are delivered at clinically relevant magnitudes. We performed bench-testing of a set of commercial ICP sensors. In our experimental setup, the ICP sensor was placed in a container with 0.9% NaCl solution. A test person was charged 0.5-10 kV, and then delivered ESD's to the sensor by touching a metal rod that was located in the container. The continuous pressure signals were recorded continuously before/after the ESD's, and the pressure readings were stored digitally using a computerized system A total of 57 sensors were tested, including 25 Codman ICP sensors and 32 Raumedic sensors. When charging the test person in the range 0.5-10 kV, typically ESD's in the range 0.5-5 kV peak pulse were delivered to the ICP sensor. Alterations in baseline pressure ≥ 2 mmHg was seen in 24 of 25 (96%) Codman sensors and in 17 of 32 (53%) Raumedic sensors. Lasting changes in baseline pressure > 10 mmHg that in the clinical setting would affect patient management, were seen frequently for both sensor types. The changes in baseline pressure were either characterized by sudden shifts or gradual drifts in baseline pressure. The baseline pressures of commercial solid ICP sensors can be altered by ESD's at discharge magnitudes that are clinically relevant. Shifts in baseline pressure change the ICP levels visualised to the physician on the monitor screen, and thereby reveal wrong ICP values, which likely represent a severe risk to the patient.

The baseline pressure of intracranial pressure (ICP) sensors can be altered by electrostatic discharges

PubMed Central

2011-01-01

Background The monitoring of intracranial pressure (ICP) has a crucial role in the surveillance of patients with brain injury. During long-term monitoring of ICP, we have seen spontaneous shifts in baseline pressure (ICP sensor zero point), which are of technical and not physiological origin. The aim of the present study was to explore whether or not baseline pressures of ICP sensors can be affected by electrostatics discharges (ESD's), when ESD's are delivered at clinically relevant magnitudes. Methods We performed bench-testing of a set of commercial ICP sensors. In our experimental setup, the ICP sensor was placed in a container with 0.9% NaCl solution. A test person was charged 0.5 - 10 kV, and then delivered ESD's to the sensor by touching a metal rod that was located in the container. The continuous pressure signals were recorded continuously before/after the ESD's, and the pressure readings were stored digitally using a computerized system Results A total of 57 sensors were tested, including 25 Codman ICP sensors and 32 Raumedic sensors. When charging the test person in the range 0.5-10 kV, typically ESD's in the range 0.5 - 5 kV peak pulse were delivered to the ICP sensor. Alterations in baseline pressure ≥ 2 mmHg was seen in 24 of 25 (96%) Codman sensors and in 17 of 32 (53%) Raumedic sensors. Lasting changes in baseline pressure > 10 mmHg that in the clinical setting would affect patient management, were seen frequently for both sensor types. The changes in baseline pressure were either characterized by sudden shifts or gradual drifts in baseline pressure. Conclusions The baseline pressures of commercial solid ICP sensors can be altered by ESD's at discharge magnitudes that are clinically relevant. Shifts in baseline pressure change the ICP levels visualised to the physician on the monitor screen, and thereby reveal wrong ICP values, which likely represent a severe risk to the patient. PMID:21859487

Fully wireless pressure sensor based on endoscopy images

NASA Astrophysics Data System (ADS)

Maeda, Yusaku; Mori, Hirohito; Nakagawa, Tomoaki; Takao, Hidekuni

2018-04-01

In this paper, the result of developing a fully wireless pressure sensor based on endoscopy images for an endoscopic surgery is reported for the first time. The sensor device has structural color with a nm-scale narrow gap, and the gap is changed by air pressure. The structural color of the sensor is acquired from camera images. Pressure detection can be realized with existing endoscope configurations only. The inner air pressure of the human body should be measured under flexible-endoscope operation using the sensor. Air pressure monitoring, has two important purposes. The first is to quantitatively measure tumor size under a constant air pressure for treatment selection. The second purpose is to prevent the endangerment of a patient due to over transmission of air. The developed sensor was evaluated, and the detection principle based on only endoscopy images has been successfully demonstrated.

Sensor for the working surface cleanliness definition in vacuum

NASA Astrophysics Data System (ADS)

Deulin, E. A.; Mashurov, S. S.; Gatsenko, A. A.

2016-07-01

Modern development of nanotechnology as one of the modern science priority directions is impossible to imagine without the use of vacuum systems and technologies. And the better the vacuum (lower the pressure), the “cleaner” we get a surface, which is very important for nanotechnology. Determination of the cleanliness of the surface or the amount of molecular layers of adsorbed gases on the working surface of the products especially in industry, where the cleanliness of the working surface is a key parameter of the technological process and has a significant influence on the output parameters of the final product is the main goal of this work.

METHOD FOR PUMPING GASES AT LOW VACUUM PRESSURES

DOEpatents

Milleron, N.

1962-06-01

A method is given for pumping overpressure "pulses" or "bursts" of gases without a significant rise in base pressure within a "gettering-type" vacuum pump having surfaces within the pumping cavity coated with or comprising clean gettering metal, e.g., Mo or Ta. The cavity is first pumped down by any convenient means to an equilibrium base pressure in the range desired, generally below 10/sup -6/ mm Hg. At this pressure, the metal immediately adsorbs overpressures or "bursts" of gases striking same with thermal motion without raising the base pressure significantiy. Desorption takes place at an equilibrium rate which, of course, is dependent upon the equilibrium pressure, and such desorbed gases are continuously removed by diffuaion pump or other pumping, whereby said overpressures or "bursts" of gases are removed without a rise in the equilibrium pressure and/or back diffusion of the gaseous pulse from the pumping cavity. (AEC)

Ultrahigh Temperature Capacitive Pressure Sensor

NASA Technical Reports Server (NTRS)

Harsh, Kevin

2014-01-01

Robust, miniaturized sensing systems are needed to improve performance, increase efficiency, and track system health status and failure modes of advanced propulsion systems. Because microsensors must operate in extremely harsh environments, there are many technical challenges involved in developing reliable systems. In addition to high temperatures and pressures, sensing systems are exposed to oxidation, corrosion, thermal shock, fatigue, fouling, and abrasive wear. In these harsh conditions, sensors must be able to withstand high flow rates, vibration, jet fuel, and exhaust. In order for existing and future aeropropulsion turbine engines to improve safety and reduce cost and emissions while controlling engine instabilities, more accurate and complete sensor information is necessary. High-temperature (300 to 1,350 C) capacitive pressure sensors are of particular interest due to their high measurement bandwidth and inherent suitability for wireless readout schemes. The objective of this project is to develop a capacitive pressure sensor based on silicon carbon nitride (SiCN), a new class of high-temperature ceramic materials, which possesses excellent mechanical and electric properties at temperatures up to 1,600 C.

Micromachined pressure sensors: Review and recent developments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eaton, W.P.; Smith, J.H.

1997-03-01

Since the discovery of piezoresistivity in silicon in the mid 1950s, silicon-based pressure sensors have been widely produced. Micromachining technology has greatly benefited from the success of the integrated circuits industry, burrowing materials, processes, and toolsets. Because of this, microelectromechanical systems (MEMS) are now poised to capture large segments of existing sensor markets and to catalyze the development of new markets. Given the emerging importance of MEMS, it is instructive to review the history of micromachined pressure sensors, and to examine new developments in the field. Pressure sensors will be the focus of this paper, starting from metal diaphragm sensorsmore » with bonded silicon strain gauges, and moving to present developments of surface-micromachined, optical, resonant, and smart pressure sensors. Considerations for diaphragm design will be discussed in detail, as well as additional considerations for capacitive and piezoresistive devices.« less

Optical detection system for MEMS-type pressure sensor

NASA Astrophysics Data System (ADS)

Sareło, K.; Górecka-Drzazga, A.; Dziuban, J. A.

2015-07-01

In this paper a special optical detection system designed for a MEMS-type (micro-electro-mechanical system) silicon pressure sensor is presented. The main part of the optical system—a detection unit with a perforated membrane—is bonded to the silicon sensor, and placed in a measuring system. An external light source illuminates the membrane of the pressure sensor. Owing to the light reflected from the deflected membrane sensor, the optical pattern consisting of light points is visible, and pressure can be estimated. The optical detection unit (20   ×   20   ×   20.4 mm3) is fabricated using microengineering techniques. Its dimensions are adjusted to the dimensions of the pressure sensor (5   ×   5 mm2 silicon membrane). Preliminary tests of the optical detection unit integrated with the silicon pressure sensor are carried out. For the membrane sensor from 15 to 60 µm thick, a repeatable detection of the differential pressure in the range of 0 to 280 kPa is achieved. The presented optical microsystem is especially suitable for the pressure measurements in a high radiation environment.

A Graphene-Based Resistive Pressure Sensor with Record-High Sensitivity in a Wide Pressure Range

PubMed Central

Tian, He; Shu, Yi; Wang, Xue-Feng; Mohammad, Mohammad Ali; Bie, Zhi; Xie, Qian-Yi; Li, Cheng; Mi, Wen-Tian; Yang, Yi; Ren, Tian-Ling

2015-01-01

Pressure sensors are a key component in electronic skin (e-skin) sensing systems. Most reported resistive pressure sensors have a high sensitivity at low pressures (<5 kPa) to enable ultra-sensitive detection. However, the sensitivity drops significantly at high pressures (>5 kPa), which is inadequate for practical applications. For example, actions like a gentle touch and object manipulation have pressures below 10 kPa, and 10–100 kPa, respectively. Maintaining a high sensitivity in a wide pressure range is in great demand. Here, a flexible, wide range and ultra-sensitive resistive pressure sensor with a foam-like structure based on laser-scribed graphene (LSG) is demonstrated. Benefitting from the large spacing between graphene layers and the unique v-shaped microstructure of the LSG, the sensitivity of the pressure sensor is as high as 0.96 kPa−1 in a wide pressure range (0 ~ 50 kPa). Considering both sensitivity and pressure sensing range, the pressure sensor developed in this work is the best among all reported pressure sensors to date. A model of the LSG pressure sensor is also established, which agrees well with the experimental results. This work indicates that laser scribed flexible graphene pressure sensors could be widely used for artificial e-skin, medical-sensing, bio-sensing and many other areas. PMID:25721159

Design, fabrication and metrological evaluation of wearable pressure sensors.

PubMed

Goy, C B; Menichetti, V; Yanicelli, L M; Lucero, J B; López, M A Gómez; Parodi, N F; Herrera, M C

2015-04-01

Pressure sensors are valuable transducers that are necessary in a huge number of medical application. However, the state of the art of compact and lightweight pressure sensors with the capability of measuring the contact pressure between two surfaces (contact pressure sensors) is very poor. In this work, several types of wearable contact pressure sensors are fabricated using different conductive textile materials and piezo-resistive films. The fabricated sensors differ in size, the textile conductor used and/or the number of layers of the sandwiched piezo-resistive film. The intention is to study, through the obtaining of their calibration curves, their metrological properties (repeatability, sensitivity and range) and determine which physical characteristics improve their ability for measuring contact pressures. It has been found that it is possible to obtain wearable contact pressure sensors through the proposed fabrication process with satisfactory repeatability, range and sensitivity; and that some of these properties can be improved by the physical characteristics of the sensors.

Semiconductor nanomembrane-based sensors for high frequency pressure measurements

NASA Astrophysics Data System (ADS)

Ruan, Hang; Kang, Yuhong; Homer, Michelle; Claus, Richard O.; Mayo, David; Sibold, Ridge; Jones, Tyler; Ng, Wing

2017-04-01

This paper demonstrates improvements on semiconductor nanomembrane based high frequency pressure sensors that utilize silicon on insulator techniques in combination with nanocomposite materials. The low-modulus, conformal nanomembrane sensor skins with integrated interconnect elements and electronic devices could be applied to vehicles or wind tunnel models for full spectrum pressure analysis. Experimental data demonstrates that: 1) silicon nanomembrane may be used as single pressure sensor transducers and elements in sensor arrays, 2) the arrays may be instrumented to map pressure over the surfaces of test articles over a range of Reynolds numbers, temperature and other environmental conditions, 3) in the high frequency range, the sensor is comparable to the commercial high frequency sensor, and 4) in the low frequency range, the sensor is much better than the commercial sensor. This supports the claim that nanomembrane pressure sensors may be used for wide bandwidth flow analysis.

40 CFR 1065.215 - Pressure transducers, temperature sensors, and dewpoint sensors.

Code of Federal Regulations, 2014 CFR

2014-07-01

... sensors, such as resistive temperature detectors (RTDs). (d) Pressure. Pressure transducers must be... chilled-surface hygrometers, which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For other applications, we recommend thin-film capacitance sensors. You may use other dewpoint...

40 CFR 1065.215 - Pressure transducers, temperature sensors, and dewpoint sensors.

Code of Federal Regulations, 2013 CFR

2013-07-01

... sensors, such as resistive temperature detectors (RTDs). (d) Pressure. Pressure transducers must be... chilled-surface hygrometers, which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For other applications, we recommend thin-film capacitance sensors. You may use other dewpoint...

40 CFR 1065.215 - Pressure transducers, temperature sensors, and dewpoint sensors.

Code of Federal Regulations, 2011 CFR

2011-07-01

... sensors, such as resistive temperature detectors (RTDs). (d) Pressure. Pressure transducers must be... chilled-surface hygrometers, which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For other applications, we recommend thin-film capacitance sensors. You may use other dewpoint...

40 CFR 1065.215 - Pressure transducers, temperature sensors, and dewpoint sensors.

Code of Federal Regulations, 2012 CFR

2012-07-01

... sensors, such as resistive temperature detectors (RTDs). (d) Pressure. Pressure transducers must be... chilled-surface hygrometers, which include chilled mirror detectors and chilled surface acoustic wave (SAW) detectors. For other applications, we recommend thin-film capacitance sensors. You may use other dewpoint...

Isolating Gas Sensor From Pressure And Temperature Effects

NASA Technical Reports Server (NTRS)

Sprinkle, Danny R.; Chen, Tony T. D.; Chaturvedi, Sushi K.

1994-01-01

Two-stage flow system enables oxygen sensor in system to measure oxygen content of low-pressure, possibly-high-temperature atmosphere in test environment while protecting sensor against possibly high temperature and fluctuations in pressure of atmosphere. Sensor for which flow system designed is zirconium oxide oxygen sensor sampling atmospheres in high-temperature wind tunnels. Also adapted to other gas-analysis instruments that must be isolated from pressure and temperature effects of test environments.

Optical fiber pressure sensors for adaptive wings

NASA Astrophysics Data System (ADS)

Duncan, Paul G.; Jones, Mark E.; Shinpaugh, Kevin A.; Poland, Stephen H.; Murphy, Kent A.; Claus, Richard O.

1997-06-01

Optical fiber pressure sensors have been developed for use on a structurally-adaptive `smart wing'; further details of the design, fabrication and testing of the smart wing concept are presented in companion papers. This paper describes the design, construction, and performance of the pressure sensor and a combined optical and electronic signal processing system implemented to permit the measurement of a large number of sensors distributed over the control surfaces of a wing. Optical fiber pressure sensors were implemented due to anticipated large electromagnetic interference signals within the operational environment. The sensors utilized the principle of the extrinsic Fabry-Perot interferometer (EFPI) already developed for the measurement of strain and temperature. Here, the cavity is created inside a micromachined hollow-core tube with a silicon diaphragm at one end. The operation of the sensor is similar to that of the EFPI strain gage also discussed in several papers at this conference. The limitations placed upon the performance of the digital signal processing system were determined by the required pressure range of the sensors and the cycle time of the control system used to adaptively modify the shape of the wing. Sensor calibration and the results of testing performed are detailed.

A simple sensing mechanism for wireless, passive pressure sensors.

PubMed

Drazan, John F; Wassick, Michael T; Dahle, Reena; Beardslee, Luke A; Cady, Nathaniel C; Ledet, Eric H

2016-08-01

We have developed a simple wireless pressure sensor that consists of only three electrically isolated components. Two conductive spirals are separated by a closed cell foam that deforms when exposed to changing pressures. This deformation changes the capacitance and thus the resonant frequency of the sensors. Prototype sensors were submerged and wirelessly interrogated while being exposed to physiologically relevant pressures from 10 to 130 mmHg. Sensors consistently exhibited a sensitivity of 4.35 kHz/mmHg which is sufficient for resolving physiologically relevant pressure changes in vivo. These simple sensors have the potential for in vivo pressure sensing.

Development of high pressure-high vacuum-high conductance piston valve for gas-filled radiation detectors

NASA Astrophysics Data System (ADS)

Prasad, D. N.; Ayyappan, R.; Kamble, L. P.; Singh, J. P.; Muralikrishna, L. V.; Alex, M.; Balagi, V.; Mukhopadhyay, P. K.

2008-05-01

Gas-filled radiation detectors need gas filling at pressures that range from few cms of mercury to as high as 25kg/cm2 at room temperature. Before gas-filling these detectors require evacuation to a vacuum of the order of ~1 × 10-5 mbar. For these operations of evacuation and gas filling a system consisting of a vacuum pump with a high vacuum gauge, gas cylinder with a pressure gauge and a valve is used. The valve has to meet the three requirements of compatibility with high-pressure and high vacuum and high conductance. A piston valve suitable for the evacuation and gas filling of radiation detectors has been designed and fabricated to meet the above requirements. The stainless steel body (80mm×160mm overall dimensions) valve with a piston arrangement has a 1/2 inch inlet/outlet opening, neoprene/viton O-ring at piston face & diameter for sealing and a knob for opening and closing the valve. The piston movement mechanism is designed to have minimum wear of sealing O-rings. The valve has been hydrostatic pressure tested up to 75bars and has Helium leak rate of less than 9.6×10-9 m bar ltr/sec in vacuum mode and 2×10-7 mbar ltr/sec in pressure mode. As compared to a commercial diaphragm valve, which needed 3 hours to evacuate a 7 litre chamber to 2.5×10-5 mbar, the new valve achieved vacuum 7.4×10-6mbar in the same time under the same conditions.

Miniature piezoresistive solid state integrated pressure sensors

NASA Technical Reports Server (NTRS)

Kahng, S. K.

1980-01-01

The characteristics of silicon pressure sensors with an ultra-small diaphragm are described. The pressure sensors utilize rectangular diaphragm as small as 0.0127 x 0.0254 cm and a p-type Wheatstone bridge consisting of diffused piezoresistive elements, 0.000254 cm by 0.00254 cm. These sensors exhibit as high as 0.5 MHz natural frequency and 1 mV/V/psi pressure sensitivity. Fabrication techniques and high frequency results from shock tube testing and low frequency comparison with microphones are presented.

Calculation Of Pneumatic Attenuation In Pressure Sensors

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A.

1991-01-01

Errors caused by attenuation of air-pressure waves in narrow tubes calculated by method based on fundamental equations of flow. Changes in ambient pressure transmitted along narrow tube to sensor. Attenuation of high-frequency components of pressure wave calculated from wave equation derived from Navier-Stokes equations of viscous flow in tube. Developed to understand and compensate for frictional attenuation in narrow tubes used to connect aircraft pressure sensors with pressure taps on affected surfaces.

40 CFR 1065.215 - Pressure transducers, temperature sensors, and dewpoint sensors.

Code of Federal Regulations, 2010 CFR

2010-07-01

... sensors, and dewpoint sensors. 1065.215 Section 1065.215 Protection of Environment ENVIRONMENTAL... Measurement of Engine Parameters and Ambient Conditions § 1065.215 Pressure transducers, temperature sensors, and dewpoint sensors. (a) Application. Use instruments as specified in this section to measure...

Ultrahigh-Sensitivity Piezoresistive Pressure Sensors for Detection of Tiny Pressure.

PubMed

Li, Hongwei; Wu, Kunjie; Xu, Zeyang; Wang, Zhongwu; Meng, Yancheng; Li, Liqiang

2018-06-20

High-sensitivity pressure sensors are crucial for the ultrasensitive touch technology and E-skin, especially at the tiny-pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to 200 kPa -1 and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa -1 using short-channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 μs), excellent reproducibility and stability, and low power consumption. Remarkably, the sensor shows excellent detection capacity in the tiny-pressure range, including light-emitting diode switching with a pressure of 7 Pa, ringtone (2-20 Pa) recognition, and ultrasensitive (0.1 Pa) electronic glove. This work represents a performance and strategic progress in the field of pressure sensing.

Carbon nanotubes based vacuum gauge

NASA Astrophysics Data System (ADS)

Rudyk, N. N.; Il'in, O. I.; Il'ina, M. V.; Fedotov, A. A.; Klimin, V. S.; Ageev, O. A.

2017-11-01

We have created an ionization type Vacuum gauge with sensor element based on an array of vertically aligned carbon nanotubes. Obtained asymmetrical current-voltage characteristics at different voltage polarity on the electrode with the CNTs. It was found that when applying a negative potential on an electrode with the CNTs, the current in the gap is higher than at a positive potential. In the pressure range of 1 ÷ 103 Torr vacuum gauge sensitivity was 6 mV/Torr (at a current of 4.5·10-5 A) and in the range of 10-5 ÷ 1 Torr was 10 mV/Torr (at a current of 1.3·10-5 A). It is shown that the energy efficiency of vacuum gauge can be increased in the case where electrode with CNT operates as an emitter of electrons.

49 CFR 393.51 - Warning signals, air pressure and vacuum gauges.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 5 2011-10-01 2011-10-01 false Warning signals, air pressure and vacuum gauges... REGULATIONS PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.51 Warning signals, air pressure... paragraphs (b), (c), (d) or (e) of this section. (b) Hydraulic brakes. Vehicles manufactured on or after...

49 CFR 393.51 - Warning signals, air pressure and vacuum gauges.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 5 2014-10-01 2014-10-01 false Warning signals, air pressure and vacuum gauges... REGULATIONS PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.51 Warning signals, air pressure... paragraphs (b), (c), (d) or (e) of this section. (b) Hydraulic brakes. Vehicles manufactured on or after...

Thermoelectric Control Of Temperatures Of Pressure Sensors

NASA Technical Reports Server (NTRS)

Burkett, Cecil G., Jr.; West, James W.; Hutchinson, Mark A.; Lawrence, Robert M.; Crum, James R.

1995-01-01

Prototype controlled-temperature enclosure containing thermoelectric devices developed to house electronically scanned array of pressure sensors. Enclosure needed because (1) temperatures of transducers in sensors must be maintained at specified set point to ensure proper operation and calibration and (2) sensors sometimes used to measure pressure in hostile environments (wind tunnels in original application) that are hotter or colder than set point. Thus, depending on temperature of pressure-measurement environment, thermoelectric devices in enclosure used to heat or cool transducers to keep them at set point.

Use of Nanocomposites for Flexible Pressure Sensors =

NASA Astrophysics Data System (ADS)

Sepulveda, Alexandra Conceicao Teixeira

Polymer nanocomposites (PNCs) are defined as polymers bonded with nanoparticles to create materiais with improved properties. The development of this type of material is rapidly emerging as a multidisciplinary research activity, since their final properties can benefit many different fields of application, namely in the development of electrical devices as studied herein. A fabrication technique to produce conductive PNCs was developed in this work and used to fabricate flexible capacitive pressure sensors. The process is based on vertically aligned-carbon nanotubes (A-CNTs) embedded in a flexible and biocompatible matrix of polydimethylsiloxane (PDMS). Thin A-CNTs/PDMS nanocomposite films ( 400 mum) were produced using wetting of as-grown A-CNTs with uncured PDMS and the resulting nanocomposites were used to fabricate flexible pressure sensors. The sensing capability of this A-CNTs/PDMS nanocomposite is attributed to the distinctive combination of mechanical flexibility and electrical properties. The fabricated nanocomposites were characterized and mechanical and electrical properties evaluated. The PDMS is significantly modified by the reinforcing A-CNT fibers, demonstrating non-isotropic (as opposed to the isotropic neat PDMS) elastic properties ali different than the PDMS (Young's modulus of 0.8 MPa), including an anisotropy ratio of 4.8 and increases in the modulus of A-CNTs/PDMS nanocomposites over PDMS by more than 900 % and 100 %, in the CNTs longitudinal and transverse directions, respectively. Regarding the electrical measurements, A-CNTs/PDMS nanocomposites presented an electrical conductivity of 0.35 Sim. The rather low conductivity does not compromise the developed capacitive sensor, but since passive telemetry is required to measure and power the sensor, solutions to overcome this problem were also studied. The configuration of the developed flexible sensor is similar to typical silicon-based capacitive pressure sensors. It is composed of three thin

Pressure-Sensor Assembly Technique

NASA Technical Reports Server (NTRS)

Pruzan, Daniel A.

2003-01-01

Nielsen Engineering & Research (NEAR) recently developed an ultrathin data acquisition system for use in turbomachinery testing at NASA Glenn Research Center. This system integrates a microelectromechanical- systems- (MEMS-) based absolute pressure sensor [0 to 50 psia (0 to 345 kPa)], temperature sensor, signal-conditioning application-specific integrated circuit (ASIC), microprocessor, and digital memory into a package which is roughly 2.8 in. (7.1 cm) long by 0.75 in. (1.9 cm) wide. Each of these components is flip-chip attached to a thin, flexible circuit board and subsequently ground and polished to achieve a total system thickness of 0.006 in. (0.15 mm). Because this instrument is so thin, it can be quickly adhered to any surface of interest where data can be collected without disrupting the flow being investigated. One issue in the development of the ultrathin data acquisition system was how to attach the MEMS pressure sensor to the circuit board in a manner which allowed the sensor s diaphragm to communicate with the ambient fluid while providing enough support for the chip to survive the grinding and polishing operations. The technique, developed by NEAR and Jabil Technology Services Group (San Jose, CA), is described below. In the approach developed, the sensor is attached to the specially designed circuit board, see Figure 1, using a modified flip-chip technique. The circular diaphragm on the left side of the sensor is used to actively measure the ambient pressure, while the diaphragm on the right is used to compensate for changes in output due to temperature variations. The circuit board is fabricated with an access hole through it so that when the completed system is installed onto a wind tunnel model (chip side down), the active diaphragm is exposed to the environment. After the sensor is flip-chip attached to the circuit board, the die is underfilled to support the chip during the subsequent grinding and polishing operations. To prevent this

A miniature fiber optic pressure sensor for intradiscal pressure measurements of rodents

NASA Astrophysics Data System (ADS)

Nesson, Silas; Yu, Miao; Hsieh, Adam H.

2007-04-01

Lower back pain continues to be a leading cause of disability in people of all ages, and has been associated with degenerative disc disease. It is well accepted that mechanical stress, among other factors, can play a role in the development of disc degeneration. Pressures generated in the intervertebral disc have been measured both in vivo and in vitro for humans and animals. However, thus far it has been difficult to measure pressure experimentally in rodent discs due to their small size. With the prevalent use of rodent tail disc models in mechanobiology, it is important to characterize the intradiscal pressures generated with externally applied stresses. In this paper, a miniature fiber optic Fabry-Perot interferometric pressure sensor with an outer diameter of 360 μm was developed to measure intradiscal pressures in rat caudal discs. A low coherence interferometer based optical system was used, which includes a broadband light source, a high-speed spectrometer, and a Fabry-Perot sensor. The sensor employs a capillary tube, a flexible, polymer diaphragm coated with titanium as a partial mirror, and a fiber tip as another mirror. The pressure induced deformation of the diaphragm results in a cavity length change of the Fabry-Perot interferometer which can be calculated from the wavelength shift of interference fringes. The sensor exhibited good linearity with small applied pressures. Our validation experiments show that owing to the small size, inserting the sensor does not disrupt the annulus fibrosus and will not alter intradiscal pressures generated. Measurements also demonstrate the feasibility of using this sensor to quantify external load intradiscal pressure relationships in small animal discs.

Downhole pressure sensor

NASA Technical Reports Server (NTRS)

Berdahl, C. M.

1980-01-01

Sensor remains accurate in spite of varying temperatures. Very accurate, sensitive, and stable downhole pressure measurements are needed for vaiety of reservoir engineering applications, such as deep petroleum reservoirs, especially gas reservoirs, and in areas of high geothermal gradient.

Residual Negative Pressure in Vacuum Tubes Might Increase the Risk of Spurious Hemolysis.

PubMed

Xiao, Tong-Tong; Zhang, Qiao-Xin; Hu, Jing; Ouyang, Hui-Zhen; Cai, Ying-Mu

2017-05-01

We planned a study to establish whether spurious hemolysis may occur when negative pressure remains in vacuum tubes. Four tubes with different vacuum levels (-54, -65, -74, and -86 kPa) were used to examine blood drawn from one healthy volunteer; the tubes were allowed to stand for different times (1, 2, 3, and 4 hours). The plasma was separated and immediately tested for free hemoglobin (FHb). Thirty patients were enrolled in a verification experiment. The degree of hemolysis observed was greater when the remaining negative pressure was higher. Significant differences were recorded in the verification experiment. The results suggest that residual negative pressure might increase the risk of spurious hemolysis.

Under Pressure: Activities with a Vacuum Pump (and Some Marshmallows) Help Students Learn about Pressure.

ERIC Educational Resources Information Center

Galus, Pamela

2002-01-01

Introduces a science demonstration that illustrates the effects of pressure and gravity on humans using a marshmallow man and a vacuum pump. Demonstrates the same concept with shaving cream, balloons, and boiling water without raising temperature. (YDS)

49 CFR 393.51 - Warning signals, air pressure and vacuum gauges.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 5 2013-10-01 2013-10-01 false Warning signals, air pressure and vacuum gauges... REGULATIONS PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.51 Warning signals, air pressure... paragraph (f), must be equipped with a signal that provides a warning to the driver when a failure occurs in...

49 CFR 393.51 - Warning signals, air pressure and vacuum gauges.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 5 2012-10-01 2012-10-01 false Warning signals, air pressure and vacuum gauges... REGULATIONS PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.51 Warning signals, air pressure... paragraph (f), must be equipped with a signal that provides a warning to the driver when a failure occurs in...

Mimicking Martian dust: An in-vacuum dust deposition system for testing the ultraviolet sensors on the Curiosity rover.

PubMed

Sobrado, J M; Martín-Soler, J; Martín-Gago, J A

2015-10-01

We have designed and developed an in-vacuum dust deposition system specifically conceived to simulate and study the effect of accumulation of Martian dust on the electronic instruments of scientific planetary exploration missions. We have used this device to characterize the dust effect on the UV sensor of the Rover Environmental Monitoring Station in the Mars science Laboratory mission of NASA in similar conditions to those found on Mars surface. The UV sensor includes six photodiodes for measuring the radiation in all UV wavelengths (direct incidence and reflected); it is placed on the body of Curiosity rover and it is severely affected by the dust deposited on it. Our experimental setup can help to estimate the duration of reliable reading of this instrument during operation. We have used an analogous of the Martian dust in chemical composition (magnetic species), color, and density, which has been characterized by X-ray spectroscopy. To ensure a Brownian motion of the dust during its fall and a homogeneous coverage on the instrumentation, the operating conditions of the vacuum vessel, determined by partial pressures and temperature, have to be modified to account for the different gravities of Mars with respect to Earth. We propose that our designed device and operational protocol can be of interest to test optoelectronic instrumentation affected by the opacity of dust, as can be the degradation of UV photodiodes in planetary exploration.

Electronically scanned pressure sensor module with in SITU calibration capability

NASA Technical Reports Server (NTRS)

Gross, C. (Inventor)

1978-01-01

This high data rate pressure sensor module helps reduce energy consumption in wind tunnel facilities without loss of measurement accuracy. The sensor module allows for nearly a two order of magnitude increase in data rates over conventional electromechanically scanned pressure sampling techniques. The module consists of 16 solid state pressure sensor chips and signal multiplexing electronics integrally mounted to a four position pressure selector switch. One of the four positions of the pressure selector switch allows the in situ calibration of the 16 pressure sensors; the three other positions allow 48 channels (three sets of 16) pressure inputs to be measured by the sensors. The small size of the sensor module will allow mounting within many wind tunnel models, thus eliminating long tube lengths and their corresponding slow pressure response.

FOREWORD: The 4th CCM International Conference on Pressure Metrology from Ultra-High Vacuum to Very High Pressures (10-9 Pa to 109 Pa)

NASA Astrophysics Data System (ADS)

Legras, Jean-Claude; Jousten, Karl; Severn, Ian

2005-12-01

The fourth CCM (Consultative Committee for Mass and related quantities) International Conference on Pressure Metrology from Ultra-High Vacuum to Very High Pressures (10-9 Pa to 109 Pa) was held at the Institute of Physics in London from 19-21 April 2005. The event, which was organized by the Low, Medium and High Pressure working groups of the CCM, was attended by in excess of one hundred participants with representatives from five continents and every regional metrology organization. The purpose of this conference is to review all the work that is devoted to the highest quality of pressure measurement by primary standards as well as the dissemination of the pressure scale. A total of 52 papers were presented orally, and 26 as posters, in sessions that covered the following topics: Latest scientific advances in pressure and vacuum metrology Innovative transfer standards, advanced sensors and new instrument development Primary (top-level) measurement standards International and regional key comparisons New approaches to calibration It is interesting the note that since the third conference in 1999 the pressure range covered has increased by two orders of magnitude to 109 Pa, to take into account more exacting scientific and industrial demands for traceable vacuum measurement. A further feature of the conference was the increased range of instrumentation and techniques used in the realization and potential realization of pressure standards. Seton Bennett, Director of International Metrology at the National Physical Laboratory, opened the conference and Andrew Wallard, Director of the Bureau International des Poids et Mesures (BIPM), gave the keynote address which described the implementation of the mutual recognition arrangement and the resulting removal of metrological barriers to international trade. Many experts have contributed significant amounts of their time to organize the event and to review the submitted papers. Thanks are due to all of these people

Tests Of Array Of Flush Pressure Sensors

NASA Technical Reports Server (NTRS)

Larson, Larry J.; Moes, Timothy R.; Siemers, Paul M., III

1992-01-01

Report describes tests of array of pressure sensors connected to small orifices flush with surface of 1/7-scale model of F-14 airplane in wind tunnel. Part of effort to determine whether pressure parameters consisting of various sums, differences, and ratios of measured pressures used to compute accurately free-stream values of stagnation pressure, static pressure, angle of attack, angle of sideslip, and mach number. Such arrays of sensors and associated processing circuitry integrated into advanced aircraft as parts of flight-monitoring and -controlling systems.

Organic electronics based pressure sensor towards intracranial pressure monitoring

NASA Astrophysics Data System (ADS)

Rai, Pratyush; Varadan, Vijay K.

2010-04-01

The intra-cranial space, which houses the brain, contains cerebrospinal fluid (CSF) that acts as a fluid suspension medium for the brain. The CSF is always in circulation, is secreted in the cranium and is drained out through ducts called epidural veins. The venous drainage system has inherent resistance to the flow. Pressure is developed inside the cranium, which is similar to a rigid compartment. Normally a pressure of 5-15 mm Hg, in excess of atmospheric pressure, is observed at different locations inside the cranium. Increase in Intra-Cranial Pressure (ICP) can be caused by change in CSF volume caused by cerebral tumors, meningitis, by edema of a head injury or diseases related to cerebral atrophy. Hence, efficient ways of monitoring ICP need to be developed. A sensor system and monitoring scheme has been discussed here. The system architecture consists of a membrane less piezoelectric pressure sensitive element, organic thin film transistor (OTFT) based signal transduction, and signal telemetry. The components were fabricated on flexible substrate and have been assembled using flip-chip packaging technology. Material science and fabrication processes, subjective to the device performance, have been discussed. Capability of the device in detecting pressure variation, within the ICP pressure range, is investigated and applicability of measurement scheme to medical conditions has been argued for. Also, applications of such a sensor-OTFT assembly for logic sensor switching and patient specific-secure monitoring system have been discussed.

Noncontact Monitoring of Respiration by Dynamic Air-Pressure Sensor.

PubMed

Takarada, Tohru; Asada, Tetsunosuke; Sumi, Yoshihisa; Higuchi, Yoshinori

2015-01-01

We have previously reported that a dynamic air-pressure sensor system allows respiratory status to be visually monitored for patients in minimally clothed condition. The dynamic air-pressure sensor measures vital information using changes in air pressure. To utilize this device in the field, we must clarify the influence of clothing conditions on measurement. The present study evaluated use of the dynamic air-pressure sensor system as a respiratory monitor that can reliably detect change in breathing patterns irrespective of clothing. Twelve healthy volunteers reclined on a dental chair positioned horizontally with the sensor pad for measuring air-pressure signals corresponding to respiration placed on the seat back of the dental chair in the central lumbar region. Respiratory measurements were taken under 2 conditions: (a) thinly clothed (subject lying directly on the sensor pad); and (b) thickly clothed (subject lying on the sensor pad covered with a pressure-reducing sheet). Air-pressure signals were recorded and time integration values for air pressure during each expiration were calculated. This information was compared with expiratory tidal volume measured simultaneously by a respirometer connected to the subject via face mask. The dynamic air-pressure sensor was able to receive the signal corresponding to respiration regardless of clothing conditions. A strong correlation was identified between expiratory tidal volume and time integration values for air pressure during each expiration for all subjects under both clothing conditions (0.840-0.988 for the thinly clothed condition and 0.867-0.992 for the thickly clothed condition). These results show that the dynamic air-pressure sensor is useful for monitoring respiratory physiology irrespective of clothing.

Size effect of optical silica microsphere pressure sensors

NASA Astrophysics Data System (ADS)

Jiao, Xinbing; Hao, Ruirui; Pan, Qian; Zhao, Xinwei; Bai, Xue

2018-07-01

Two types of optical pressure sensors with silica microspheres are proposed. The size effect of optical silica microsphere pressure sensors is studied by using a single-wavelength laser beam and polarimeters. The silica microspheres with diameters of 1.0 μm, 1.5 μm and 2.0 μm are prepared on garnet substrates by a self-assembly method. The pressure and the optical properties of the silica microspheres are measured by a resistance strain sensor and Thorlabs Stokes polarimeters as a function of the external direct current (DC) voltage. The optical silica microsphere sensor in transmission mode is suitable for pressure measuring. The results show that the pressure increases, while the diameter of the silica microspheres decreases. The maximum internal pressure can reach up to 7.3 × 107 Pa when the diameter of the silica microspheres is 1.0 μm.

Pressure distribution along the AGS vacuum chambers with new types of pump out conduits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nayak, S.; Mapes, M.; Smart, L.

2015-10-28

The AGS HEBT and ring vacuum system is monitored by the discharge current of the magnet ion pumps, which is proportional to the pressure at the inlet port of these ion pumps. The discharge current is measured and suitably calibrated to indicate the ion pump pressure. In order to calculate the vacuum chamber pressure from the ion pump pressure, a detailed analysis is essential to compute their difference in different scenarios. Such analysis has been carried out numerically in the past for the system with the older type of pump out conduits, and similar analysis using FEM in ANSYS ismore » presented in this paper with the newer type of pump out conduit.« less

A Ubiquitous Blood Pressure Sensor Worn at the Ear

NASA Astrophysics Data System (ADS)

Koizumi, Hiroshi; Shimada, Junichi; Uenishi, Yuji; Tochikubo, Osamu

2009-12-01

Blood pressure (BP) measurement and BP control are important for the prevention of lifestyle diseases, especially hypertension, which can lead to more serious conditions, such as cardiac infarction and cerebral apoplexy. The purpose of our study is to develop a ubiquitous blood pressure sensor that is more comfortable and less disruptive of users' daily activities than conventional blood pressure sensors. Our developed sensor is worn at an ear orifice and measures blood pressure at the tragus. This paper describes the concept, configuration, and the optical and electronic details of the developed ear-worn blood pressure sensor and presents preliminary evaluation results. The developed sensor causes almost no discomfort and produces signals whose quality is high enough for detecting BP at an ear, making it suitable for ubiquitous usage.

Method for making a dynamic pressure sensor and a pressure sensor made according to the method

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J. (Inventor); Robbins, William E. (Inventor); Robins, Glenn M. (Inventor)

1994-01-01

A method for providing a perfectly flat top with a sharp edge on a dynamic pressure sensor using a cup-shaped stretched membrane as a sensing element is described. First, metal is deposited on the membrane and surrounding areas. Next, the side wall of the pressure sensor with the deposited metal is machined to a predetermined size. Finally, deposited metal is removed from the top of the membrane in small steps, by machining or lapping while the pressure sensor is mounted in a jig or the wall of a test object, until the true top surface of the membrane appears. A thin indicator layer having a color contrasting with the color of the membrane may be applied to the top of the membrane before metal is deposited to facilitate the determination of when to stop metal removal from the top surface of the membrane.

High precision silicon piezo resistive SMART pressure sensor

NASA Astrophysics Data System (ADS)

Brown, Rod

2005-01-01

Instruments for test and calibration require a pressure sensor that is precise and stable. Market forces also dictate a move away from single measurand test equipment and, certainly in the case of pressure, away from single range equipment. A pressure `module' is required which excels in pressure measurement but is interchangble with sensors for other measurands. A communications interface for such a sensor has been specified. Instrument Digital Output Sensor (IDOS) that permits this interchanagability and allows the sensor to be inside or outside the measuring instrument. This paper covers the design and specification of a silicon diaphragm piezo resistive SMART sensor using this interface. A brief history of instrument sensors will be given to establish the background to this development. Design choices of the silicon doping, bridge energisation method, temperature sensing, signal conversion, data processing, compensation method, communications interface will be discussed. The physical format of the `in-instrument' version will be shown and then extended to the packaging design for the external version. Test results will show the accuracy achieved exceeds the target of 0.01%FS over a range of temperatures.

Flexible pressure sensors for burnt skin patient monitoring

NASA Astrophysics Data System (ADS)

Hong, Gwang-Wook; Kim, Se-Hoon; Kim, Joo-Hyung

2015-04-01

To monitor hypertrophic scars in burnt skin we proposed and demonstrated a hybrid polymer/carbon tube-based flexible pressure sensor. To monitor the pressure on skin by measurement, we were focusing on the fabrication of a well-defined hybrid polydimethylsiloxsane/functionalized multi-walled carbon tube array formed on the patterned interdigital transducer in a controllable way for the application of flexible pressure sensing devices. As a result, the detection at the pressure of 20 mmHg is achieved, which is a suggested optimal value of resistance for sensing pressure. It should be noted that the achieved value of resistance at the pressure of 20 mmHg is highly desirable for the further development of sensitive flexible pressure sensors. In addition we demonstrate a feasibility of a wearable pressure sensor which can be in real-time detection of local pressure by wireless communication module. Keywords:

Cryogenic Multichannel Pressure Sensor With Electronic Scanning

NASA Technical Reports Server (NTRS)

Hopson, Purnell, Jr.; Chapman, John J.; Kruse, Nancy M. H.

1994-01-01

Array of pressure sensors operates reliably and repeatably over wide temperature range, extending from normal boiling point of water down to boiling point of nitrogen. Sensors accurate and repeat to within 0.1 percent. Operate for 12 months without need for recalibration. Array scanned electronically, sensor readings multiplexed and sent to desktop computer for processing and storage. Used to measure distributions of pressure in research on boundary layers at high Reynolds numbers, achieved by low temperatures.

Fiber optic plantar pressure/shear sensor

NASA Astrophysics Data System (ADS)

Soetanto, William; Nguyen, Ngoc T.; Wang, Wei-Chih

2011-04-01

A full-scale foot pressure/shear sensor that has been developed to help diagnose the cause of ulcer formation in diabetic patients is presented. The design involves a tactile sensor array using intersecting optical fibers embedded in soft elastomer. The basic configuration incorporates a mesh that is comprised of two sets of parallel optical fiber plane; the planes are configured so the parallel rows of fiber of the top and bottom planes are perpendicular to each other. Threedimensional information is determined by measuring the loss of light from each of the waveguide to map the overall pressure distribution and the shifting of the layers relative to each other. In this paper we will present the latest development on the fiber optic plantar pressure/shear sensor which can measure normal force up from 19.09 kPa to 1000 kPa.

Edwards nXDS15iC Vacuum Scroll Pump Pressure Testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sessions, H.; Morgan, G. A.

2013-07-17

The SRNL High Pressure Laboratory performed testing on an Edwards Model nXDS15iC Vacuum Scroll Pump on July 10th and 11th of 2013 at 723-A. This testing was done in an attempt to obtain initial compression ratio information for the nXDS15iC pump, with compression ratio defined as discharge pressure of the pump divided by suction pressure. Pressure burst testing was also done on the pump to determine its design pressure for pressure safety reasons. The Edwards nXDS15iC pump is being evaluated by SRNL for use part of the SHINE project being executed by SRNL.

Development of two-dimensional interdigitated center of pressure sensor

NASA Astrophysics Data System (ADS)

Yoo, Byungseok; Pines, Darryll J.

2017-12-01

This paper presents the development of a two-dimensional (2D) flexible patch sensor to detect and monitor the center of pressure (CoP) location and the total magnitude of a spatially distributed pressure to the specific surface areas of engineering structures. The CoP sensor with the contact mode induced by a pressure distribution was formulated by force sensitive resistor technology and was mainly composed of a thin conductive polymer layer, adhesive spacers, and two interdigitated patterned electrode films with unique sensing aperture shadings. By properly mapping the interdigitated electrode patterns to the top and bottom surfaces of the conductive polymer, the proposed sensor ideally enables to measure an overall applied pressure level and its centroid location within a predetermined sensing region in real-time. The CoP sensor containing 36 sensing sections within a dimension of around 3 × 3 inches was prototyped and experimentally investigated to verify its capability to identify the CoP location and magnitude due to the presence of a permanent magnet-based local pressure distribution. Only five electric wires connected to the CoP sensor to inspect the pressure-sensing positions of 36 segments. The evaluation results of the measured sensor data demonstrate good agreements with the actual test parameters such as the total pressure and its centroid position with about 5% locational error. However, to provide accurate information on the overall pressure range, the compensation factors must be determined and applied to the individual sensing sections of the sensor.

A platform-based foot pressure/shear sensor

NASA Astrophysics Data System (ADS)

Chang, Chun-Te; Liu, Chao Shih; Soetanto, William; Wang, Wei-Chih

2012-04-01

The proposed research is aimed at developing, fabricating and implementing a flexible fiber optic bend loss sensor for the measurement of plantar pressure and shear stress for diabetic patients. The successful development of the sensor will greatly impact the study of diabetic foot ulcers by allowing clinicians to measure a parameter (namely, shear stress) that has been implicated in ulceration, but heretofore, has not been routinely quantified on high risk patients. A full-scale foot pressure/shear sensor involves a tactile sensor array using intersecting optical waveguides is presented. The basic configuration of the optical sensor systems incorporates a mesh that is comprised of two sets of parallel optical waveguide planes; the planes are configured so the parallel rows of waveguides of the top and bottom planes are perpendicular to each other. The planes are sandwiched together creating one sensing sheet. Two-dimensional information is determined by measuring the loss of light from each of the waveguide to map the overall pressure distribution. The shifting of the layers relative to each other allows determination of the shear stress in the plane of the sensor. This paper presents latest development and improvement in the sensors design. Fabrication and results from the latest tests will be described.

Mimicking Martian dust: An in-vacuum dust deposition system for testing the ultraviolet sensors on the Curiosity rover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobrado, J. M., E-mail: sobradovj@inta.es; Martín-Soler, J.; Martín-Gago, J. A.

We have designed and developed an in-vacuum dust deposition system specifically conceived to simulate and study the effect of accumulation of Martian dust on the electronic instruments of scientific planetary exploration missions. We have used this device to characterize the dust effect on the UV sensor of the Rover Environmental Monitoring Station in the Mars science Laboratory mission of NASA in similar conditions to those found on Mars surface. The UV sensor includes six photodiodes for measuring the radiation in all UV wavelengths (direct incidence and reflected); it is placed on the body of Curiosity rover and it is severelymore » affected by the dust deposited on it. Our experimental setup can help to estimate the duration of reliable reading of this instrument during operation. We have used an analogous of the Martian dust in chemical composition (magnetic species), color, and density, which has been characterized by X-ray spectroscopy. To ensure a Brownian motion of the dust during its fall and a homogeneous coverage on the instrumentation, the operating conditions of the vacuum vessel, determined by partial pressures and temperature, have to be modified to account for the different gravities of Mars with respect to Earth. We propose that our designed device and operational protocol can be of interest to test optoelectronic instrumentation affected by the opacity of dust, as can be the degradation of UV photodiodes in planetary exploration.« less

Peristaltic pump-based low range pressure sensor calibration system

NASA Astrophysics Data System (ADS)

Vinayakumar, K. B.; Naveen Kumar, G.; Nayak, M. M.; Dinesh, N. S.; Rajanna, K.

2015-11-01

Peristaltic pumps were normally used to pump liquids in several chemical and biological applications. In the present study, a peristaltic pump was used to pressurize the chamber (positive as well negative pressures) using atmospheric air. In the present paper, we discuss the development and performance study of an automatic pressurization system to calibrate low range (millibar) pressure sensors. The system includes a peristaltic pump, calibrated pressure sensor (master sensor), pressure chamber, and the control electronics. An in-house developed peristaltic pump was used to pressurize the chamber. A closed loop control system has been developed to detect and adjust the pressure leaks in the chamber. The complete system has been integrated into a portable product. The system performance has been studied for a step response and steady state errors. The system is portable, free from oil contaminants, and consumes less power compared to existing pressure calibration systems. The veracity of the system was verified by calibrating an unknown diaphragm based pressure sensor and the results obtained were satisfactory.

Optical Pressure-Temperature Sensor for a Combustion Chamber

NASA Technical Reports Server (NTRS)

Wiley, John; Korman, Valentin; Gregory, Don

2008-01-01

A compact sensor for measuring temperature and pressure in a combusti on chamber has been proposed. The proposed sensor would include two optically birefringent, transmissive crystalline wedges: one of sapph ire (Al2O3) and one of magnesium oxide (MgO), the optical properties of both of which vary with temperature and pressure. The wedges wou ld be separated by a vapor-deposited thin-film transducer, which wou ld be primarily temperaturesensitive (in contradistinction to pressur e- sensitive) when attached to a crystalline substrate. The sensor w ould be housed in a rugged probe to survive the extreme temperatures and pressures in a combustion chamber.

Optical Fibre Pressure Sensors in Medical Applications.

PubMed

Poeggel, Sven; Tosi, Daniele; Duraibabu, DineshBabu; Leen, Gabriel; McGrath, Deirdre; Lewis, Elfed

2015-07-15

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.

Optical Fibre Pressure Sensors in Medical Applications

PubMed Central

Poeggel, Sven; Tosi, Daniele; Duraibabu, DineshBabu; Leen, Gabriel; McGrath, Deirdre; Lewis, Elfed

2015-01-01

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas. PMID:26184228

Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics.

PubMed

Lee, Jaehong; Kwon, Hyukho; Seo, Jungmok; Shin, Sera; Koo, Ja Hoon; Pang, Changhyun; Son, Seungbae; Kim, Jae Hyung; Jang, Yong Hoon; Kim, Dae Eun; Lee, Taeyoon

2015-04-17

A flexible and sensitive textile-based pressure sensor is developed using highly conductive fibers coated with dielectric rubber materials. The pressure sensor exhibits superior sensitivity, very fast response time, and high stability, compared with previous textile-based pressure sensors. By using a weaving method, the pressure sensor can be applied to make smart gloves and clothes that can control machines wirelessly as human-machine interfaces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A miniature pressure sensor for blast event evaluation

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Wenhui; Tian, Ye; Niezrecki, Christopher; Wang, Xingwei

2011-06-01

Traumatic brain injury (TBI) is a great potential threat to people who deal with explosive devices. Protection from TBI has attracted more and more interest. Great efforts have been taken to the studies on the understanding of the propagation of the blast events and its effect on TBI. However, one of the biggest challenges is that the current available pressure sensors are not fast enough to capture the blast wave especially the transient period. This paper reports an ultrafast pressure sensor that could be very useful for analysis of the fast changing blast signal. The sensor is based on Fabry-Perot (FP) principle. It uses a 45º angle polished fiber sitting in a V-groove on a silicon chip. The endface of the angle polished fiber and the diaphragm which is lifted off on the side wall of the V-groove form the FP cavity. The sensor is very small and can be mounted on different locations of a helmet to measure blast pressure simultaneously. The tests were conducted at Natick Soldier Research, Development, and Engineering Center (NSRDEC) in Natick, MA. The sensors were mounted in a shock tube, side by side with the reference sensors, to measure a rapidly increased pressure. The results demonstrated that our sensors' responses agreed well with those from the electrical reference sensors and their response time is comparable.

Fast pressure-sensor system

NASA Technical Reports Server (NTRS)

Gross, C.

1976-01-01

Miniature silicon-diaphragm sensors and signal multiplexer are mounted to ganged zero-operate-calibrate pressure selector switches. Device allows in-situ calibration, can be computer controlled, and measures at approximately 10,000 readings per second.

Peristaltic pump-based low range pressure sensor calibration system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vinayakumar, K. B.; Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore 5600012; Naveen Kumar, G.

2015-11-15

Peristaltic pumps were normally used to pump liquids in several chemical and biological applications. In the present study, a peristaltic pump was used to pressurize the chamber (positive as well negative pressures) using atmospheric air. In the present paper, we discuss the development and performance study of an automatic pressurization system to calibrate low range (millibar) pressure sensors. The system includes a peristaltic pump, calibrated pressure sensor (master sensor), pressure chamber, and the control electronics. An in-house developed peristaltic pump was used to pressurize the chamber. A closed loop control system has been developed to detect and adjust the pressuremore » leaks in the chamber. The complete system has been integrated into a portable product. The system performance has been studied for a step response and steady state errors. The system is portable, free from oil contaminants, and consumes less power compared to existing pressure calibration systems. The veracity of the system was verified by calibrating an unknown diaphragm based pressure sensor and the results obtained were satisfactory.« less

Optical fiber pressure sensor based on fiber Bragg grating

NASA Astrophysics Data System (ADS)

Song, Dongcao

In oil field, it is important to measure the high pressure and temperature for down-hole oil exploration and well-logging, the available traditional electronic sensor is challenged due to the harsh, flammable environment. Recently, applications based on fiber Bragg grating (FBG) sensor in the oil industry have become a popular research because of its distinguishing advantages such as electrically passive operation, immunity to electromagnetic interference, high resolution, insensitivity to optical power fluctuation etc. This thesis is divided into two main sections. In the first section, the design of high pressure sensor based on FBG is described. Several sensing elements based on FBG for high pressure measurements have been proposed, for example bulk-modulus or free elastic modulus. But the structure of bulk-modulus and free elastic modulus is relatively complex and not easy to fabricate. In addition, the pressure sensitivity is not high and the repeatability of the structure has not been investigated. In this thesis, a novel host material of carbon fiber laminated composite (CFLC) for high pressure sensing is proposed. The mechanical characteristics including principal moduli in three directions and the shape repeatability are investigated. Because of it's Young's modulus in one direction and anisotropic characteristics, the pressure sensor made by CFLC has excellent sensitivity. This said structure can be used in very high pressure measurement due to carbon fiber composite's excellent shape repetition even under high pressure. The experimental results show high pressure sensitivity of 0.101nm/MPa and high pressure measurement up to 70MPa. A pressure sensor based on CFLC and FBG with temperature compensation has been designed. In the second section, the design of low pressure sensor based on FBG is demonstrated. Due to the trade off between measurement range and sensitivity, a sensor for lower pressure range needs more sensitivity. A novel material of carbon

A Manganin Thin Film Ultra-High Pressure Sensor for Microscale Detonation Pressure Measurement

PubMed Central

Zhang, Guodong; Zhao, Yulong; Zhao, Yun; Wang, Xinchen; Ren, Wei; Li, Hui; Zhao, You

2018-01-01

With the development of energetic materials (EMs) and microelectromechanical systems (MEMS) initiating explosive devices, the measurement of detonation pressure generated by EMs in the microscale has become a pressing need. This paper develops a manganin thin film ultra-high pressure sensor based on MEMS technology for measuring the output pressure from micro-detonator. A reliable coefficient is proposed for designing the sensor’s sensitive element better. The sensor employs sandwich structure: the substrate uses a 0.5 mm thick alumina ceramic, the manganin sensitive element with a size of 0.2 mm × 0.1 mm × 2 μm and copper electrodes of 2 μm thick are sputtered sequentially on the substrate, and a 25 μm thick insulating layer of polyimide is wrapped on the sensitive element. The static test shows that the piezoresistive coefficient of manganin thin film is 0.0125 GPa−1. The dynamic experiment indicates that the detonation pressure of micro-detonator is 12.66 GPa, and the response time of the sensor is 37 ns. In a word, the sensor developed in this study is suitable for measuring ultra-high pressure in microscale and has a shorter response time than that of foil-like manganin gauges. Simultaneously, this study could be beneficial to research on ultra-high-pressure sensors with smaller size. PMID:29494519

A Micromachined Capacitive Pressure Sensor Using a Cavity-Less Structure with Bulk-Metal/Elastomer Layers and Its Wireless Telemetry Application

PubMed Central

Takahata, Kenichi; Gianchandani, Yogesh B.

2008-01-01

This paper reports a micromachined capacitive pressure sensor intended for applications that require mechanical robustness. The device is constructed with two micromachined metal plates and an intermediate polymer layer that is soft enough to deform in a target pressure range. The plates are formed of micromachined stainless steel fabricated by batch-compatible micro-electro-discharge machining. A polyurethane room-temperature-vulcanizing liquid rubber of 38-μm thickness is used as the deformable material. This structure eliminates both the vacuum cavity and the associated lead transfer challenges common to micromachined capacitive pressure sensors. For frequency-based interrogation of the capacitance, passive inductor-capacitor tanks are fabricated by combining the capacitive sensor with an inductive coil. The coil has 40 turns of a 127-μm-diameter copper wire. Wireless sensing is demonstrated in liquid by monitoring the variation in the resonant frequency of the tank via an external coil that is magnetically coupled with the tank. The sensitivity at room temperature is measured to be 23-33 ppm/KPa over a dynamic range of 340 KPa, which is shown to match a theoretical estimation. Temperature dependence of the tank is experimentally evaluated. PMID:27879824

Acoustic Detection Of Loose Particles In Pressure Sensors

NASA Technical Reports Server (NTRS)

Kwok, Lloyd C.

1995-01-01

Particle-impact-noise-detector (PIND) apparatus used in conjunction with computer program analyzing output of apparatus to detect extraneous particles trapped in pressure sensors. PIND tester essentially shaker equipped with microphone measuring noise in pressure sensor or other object being shaken. Shaker applies controlled vibration. Output of microphone recorded and expressed in terms of voltage, yielding history of noise subsequently processed by computer program. Data taken at sampling rate sufficiently high to enable identification of all impacts of particles on sensor diaphragm and on inner surfaces of sensor cavities.

An Universal packaging technique for low-drift implantable pressure sensors.

PubMed

Kim, Albert; Powell, Charles R; Ziaie, Babak

2016-04-01

Monitoring bodily pressures provide valuable diagnostic and prognostic information. In particular, long-term measurement through implantable sensors is highly desirable in situations where percutaneous access can be complicated or dangerous (e.g., intracranial pressure in hydrocephalic patients). In spite of decades of progress in the fabrication of miniature solid-state pressure sensors, sensor drift has so far severely limited their application in implantable systems. In this paper, we report on a universal packaging technique for reducing the sensor drift. The described method isolates the pressure sensor from a major source of drift, i.e., contact with the aqueous surrounding environment, by encasing the sensor in a silicone-filled medical-grade polyurethane balloon. In-vitro soak tests for 100 days using commercial micromachined piezoresistive pressure sensors demonstrate a stable operation with the output remaining within 1.8 cmH2O (1.3 mmHg) of a reference pressure transducer. Under similar test conditions, a non-isolated sensor fluctuates between 10 and 20 cmH2O (7.4-14.7 mmHg) of the reference, without ever settling to a stable operation regime. Implantation in Ossabow pigs demonstrate the robustness of the package and its in-vivo efficacy in reducing the baseline drift.

An Annular Mechanical Temperature Compensation Structure for Gas-Sealed Capacitive Pressure Sensor

PubMed Central

Hao, Xiuchun; Jiang, Yonggang; Takao, Hidekuni; Maenaka, Kazusuke; Higuchi, Kohei

2012-01-01

A novel gas-sealed capacitive pressure sensor with a temperature compensation structure is reported. The pressure sensor is sealed by Au-Au diffusion bonding under a nitrogen ambient with a pressure of 100 kPa and integrated with a platinum resistor-based temperature sensor for human activity monitoring applications. The capacitance-pressure and capacitance-temperature characteristics of the gas-sealed capacitive pressure sensor without temperature compensation structure are calculated. It is found by simulation that a ring-shaped structure on the diaphragm of the pressure sensor can mechanically suppress the thermal expansion effect of the sealed gas in the cavity. Pressure sensors without/with temperature compensation structures are fabricated and measured. Through measured results, it is verified that the calculation model is accurate. Using the compensation structures with a 900 μm inner radius, the measured temperature coefficient is much reduced as compared to that of the pressure sensor without compensation. The sensitivities of the pressure sensor before and after compensation are almost the same in the pressure range from 80 kPa to 100 kPa. PMID:22969385

Fiber-linked interferometric pressure sensor

NASA Technical Reports Server (NTRS)

Beheim, G.; Fritsch, K.; Poorman, R. N.

1987-01-01

A fiber-optic pressure sensor is described which uses a diaphragm to modulate the mirror separation of a Fabry-Perot cavity (the sensing cavity). A multimode optical fiber delivers broadband light to the sensing cavity and returns the spectrally modulated light which the cavity reflects. The sensor's output spectrum is analyzed using a tunable Fabry-Perot cavity (the reference cavity) to determine the mismatch in the mirror separations of the two cavities. An electronic servo control uses this result to cause the mirror separation of the reference cavity to equal that of the sensing cavity. The displacement of the pressure-sensing diaphragm is then obtained by measuring the capacitance of the reference cavity's metal-coated mirrors. Relative to other fiber-optic sensors, an important advantage of this instrument is its high immunity to the effects of variations in both the transmissivity of the fiber link and the wavelength of the optical source.

Fiber-Optic Pressure Sensor With Dynamic Demodulation Developed

NASA Technical Reports Server (NTRS)

Lekki, John D.

2002-01-01

Researchers at the NASA Glenn Research Center developed in-house a method to detect pressure fluctuations using a fiber-optic sensor and dynamic signal processing. This work was in support of the Intelligent Systems Controls and Operations project under NASA's Information Technology Base Research Program. We constructed an optical pressure sensor by attaching a fiber-optic Bragg grating to a flexible membrane and then adhering the membrane to one end of a small cylinder. The other end of the cylinder was left open and exposed to pressure variations from a pulsed air jet. These pressure variations flexed the membrane, inducing a strain in the fiber-optic grating. This strain was read out optically with a dynamic spectrometer to record changes in the wavelength of light reflected from the grating. The dynamic spectrometer was built in-house to detect very small wavelength shifts induced by the pressure fluctuations. The spectrometer is an unbalanced interferometer specifically designed for maximum sensitivity to wavelength shifts. An optimum pathlength difference, which was determined empirically, resulted in a 14-percent sensitivity improvement over theoretically predicted path-length differences. This difference is suspected to be from uncertainty about the spectral power difference of the signal reflected from the Bragg grating. The figure shows the output of the dynamic spectrometer as the sensor was exposed to a nominally 2-kPa peak-to-peak square-wave pressure fluctuation. Good tracking, sensitivity, and signal-to-noise ratios are evident even though the sensor was constructed as a proof-of-concept and was not optimized in any way. Therefore the fiber-optic Bragg grating, which is normally considered a good candidate as a strain or temperature sensor, also has been shown to be a good candidate for a dynamic pressure sensor.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges.

PubMed

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-03-31

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ∼3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges

NASA Astrophysics Data System (ADS)

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-03-01

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ~3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges

PubMed Central

Shin, Sung-Ho; Ji, Sangyoon; Choi, Seiho; Pyo, Kyoung-Hee; Wan An, Byeong; Park, Jihun; Kim, Joohee; Kim, Ju-Young; Lee, Ki-Suk; Kwon, Soon-Yong; Heo, Jaeyeong; Park, Byong-Guk; Park, Jang-Ung

2017-01-01

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ∼3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics. PMID:28361867

Observation of Live Ticks (Haemaphysalis flava) by Scanning Electron Microscopy under High Vacuum Pressure

PubMed Central

Ishigaki, Yasuhito; Nakamura, Yuka; Oikawa, Yosaburo; Yano, Yasuhiro; Kuwabata, Susumu; Nakagawa, Hideaki; Tomosugi, Naohisa; Takegami, Tsutomu

2012-01-01

Scanning electron microscopes (SEM), which image sample surfaces by scanning with an electron beam, are widely used for steric observations of resting samples in basic and applied biology. Various conventional methods exist for SEM sample preparation. However, conventional SEM is not a good tool to observe living organisms because of the associated exposure to high vacuum pressure and electron beam radiation. Here we attempted SEM observations of live ticks. During 1.5×10−3 Pa vacuum pressure and electron beam irradiation with accelerated voltages (2–5 kV), many ticks remained alive and moved their legs. After 30-min observation, we removed the ticks from the SEM stage; they could walk actively under atmospheric pressure. When we tested 20 ticks (8 female adults and 12 nymphs), they survived for two days after SEM observation. These results indicate the resistance of ticks against SEM observation. Our second survival test showed that the electron beam, not vacuum conditions, results in tick death. Moreover, we describe the reaction of their legs to electron beam exposure. These findings open the new possibility of SEM observation of living organisms and showed the resistance of living ticks to vacuum condition in SEM. These data also indicate, for the first time, the usefulness of tick as a model system for biology under extreme condition. PMID:22431980

Non-Intrusive Pressure/Multipurpose Sensor and Method

NASA Technical Reports Server (NTRS)

Smith, William C. (Inventor)

2001-01-01

Method and apparatus are provided for determining pressure using a non-intrusive sensor that is easily attachable to the plumbing of a pressurized system. A bent mode implementation and a hoop mode implementation of the invention are disclosed. Each of these implementations is able to nonintrusively measure pressure while fluid is flowing. As well, each implementation may be used to measure mass flow rate simultaneously with pressure. An ultra low noise control system is provided for making pressure measurements during gas flow. The control system includes two tunable digital bandpass filters with center frequencies that are responsive to a clock frequency. The clock frequency is divided by a factor of N to produce a driving vibrational signal for resonating a metal sensor section.

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.

Fiber optic photoelastic pressure sensor for high temperature gases

NASA Technical Reports Server (NTRS)

Wesson, Laurence N.; Redner, Alex S.; Baumbick, Robert J.

1990-01-01

A novel fiber optic pressure sensor based on the photoelastic effects has been developed for extremely high temperature gases. At temperatures varying from 25 to 650 C, the sensor experiences no change in the peak pressure of the transfer function and only a 10 percent drop in dynamic range. Refinement of the sensor has resulted in an optoelectronic interface and processor software which can calculate pressure values within 1 percent of full scale at any temperature within the full calibrated temperature range.

Fiber optic pressure sensors in skin-friction measurements

NASA Technical Reports Server (NTRS)

Kidwell, R.

1985-01-01

Fiber optic lever pressure sensors intended for use in a low speed wind tunnel environment were designed, constructed and tested for the measurement of normal and shear displacements associated with the pressures acting on a flat aluminum plate. On-site tests performed along with several static and dynamic measurements made have established that, with proper modifications and improvements, the design concepts are acceptable and can be utilized for their intended use. Several elastomers were investigated for use in sensors and for their incorporation into these sensors. Design and assembly techniques for probes and complete sensors were developed.

Design optimization and fabrication of a novel structural piezoresistive pressure sensor for micro-pressure measurement

NASA Astrophysics Data System (ADS)

Li, Chuang; Cordovilla, Francisco; Ocaña, José L.

2018-01-01

This paper presents a novel structural piezoresistive pressure sensor with a four-beams-bossed-membrane (FBBM) structure that consisted of four short beams and a central mass to measure micro-pressure. The proposed structure can alleviate the contradiction between sensitivity and linearity to realize the micro measurement with high accuracy. In this study, the design, fabrication and test of the sensor are involved. By utilizing the finite element analysis (FEA) to analyze the stress distribution of sensitive elements and subsequently deducing the relationships between structural dimensions and mechanical performance, the optimization process makes the sensor achieve a higher sensitivity and a lower pressure nonlinearity. Based on the deduced equations, a series of optimized FBBM structure dimensions are ultimately determined. The designed sensor is fabricated on a silicon wafer by using traditional MEMS bulk-micromachining and anodic bonding technology. Experimental results show that the sensor achieves the sensitivity of 4.65 mV/V/kPa and pressure nonlinearity of 0.25% FSS in the operating range of 0-5 kPa at room temperature, indicating that this novel structure sensor can be applied in measuring the absolute micro pressure lower than 5 kPa.

Discrete sensors distribution for accurate plantar pressure analyses.

PubMed

Claverie, Laetitia; Ille, Anne; Moretto, Pierre

2016-12-01

The aim of this study was to determine the distribution of discrete sensors under the footprint for accurate plantar pressure analyses. For this purpose, two different sensor layouts have been tested and compared, to determine which was the most accurate to monitor plantar pressure with wireless devices in research and/or clinical practice. Ten healthy volunteers participated in the study (age range: 23-58 years). The barycenter of pressures (BoP) determined from the plantar pressure system (W-inshoe®) was compared to the center of pressures (CoP) determined from a force platform (AMTI) in the medial-lateral (ML) and anterior-posterior (AP) directions. Then, the vertical ground reaction force (vGRF) obtained from both W-inshoe® and force platform was compared for both layouts for each subject. The BoP and vGRF determined from the plantar pressure system data showed good correlation (SCC) with those determined from the force platform data, notably for the second sensor organization (ML SCC= 0.95; AP SCC=0.99; vGRF SCC=0.91). The study demonstrates that an adjusted placement of removable sensors is key to accurate plantar pressure analyses. These results are promising for a plantar pressure recording outside clinical or laboratory settings, for long time monitoring, real time feedback or for whatever activity requiring a low-cost system. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

The Effect of Oxygen Partial Pressure on Microstructure and Properties of Fe40Al Alloy Sintered under Vacuum

PubMed Central

Siemiaszko, Dariusz; Kowalska, Beata; Jóźwik, Paweł; Kwiatkowska, Monika

2015-01-01

This paper presents the results of studies on the influence of oxygen partial pressure (vacuum level in the chamber) on the properties of FeAl intermetallics. One of the problems in the application of classical methods of prepared Fe-Al intermetallic is the occurrence of oxides. Applying a vacuum during sintering should reduce this effect. In order to analyze the effect of oxygen partial pressure on sample properties, five samples were processed (by a pressure-assisted induction sintering—PAIS method) under the following pressures: 3, 8, 30, 80, and 300 mbar (corresponding to oxygen partial pressures of 0.63, 1.68, 6.3, 16.8, and 63 mbar, respectively). The chemical and phase composition, hardness, density, and microstructure observations indicate that applying a vacuum significantly impacts intermetallic samples. The compact sintered at pressure 3 mbar is characterized by the most homogeneous microstructure, the highest density, high hardness, and nearly homogeneous chemical composition. PMID:28788015

Touch Sensor Responds to Contact Pressure

NASA Technical Reports Server (NTRS)

Bejczy, A. K.

1982-01-01

Optical tactile sensor for mechanical hands senses contact pressure via change in light reflected from an elastic covering. Pressure against a cell cover causes distortion, which changes internal reflection of light. Change is sensed by detector, and output signal informs operator of contact. The greater the pressure and distortion, the greater the change in light reflection.

Flexible Ferroelectric Sensors with Ultrahigh Pressure Sensitivity and Linear Response over Exceptionally Broad Pressure Range.

PubMed

Lee, Youngoh; Park, Jonghwa; Cho, Soowon; Shin, Young-Eun; Lee, Hochan; Kim, Jinyoung; Myoung, Jinyoung; Cho, Seungse; Kang, Saewon; Baig, Chunggi; Ko, Hyunhyub

2018-04-24

Flexible pressure sensors with a high sensitivity over a broad linear range can simplify wearable sensing systems without additional signal processing for the linear output, enabling device miniaturization and low power consumption. Here, we demonstrate a flexible ferroelectric sensor with ultrahigh pressure sensitivity and linear response over an exceptionally broad pressure range based on the material and structural design of ferroelectric composites with a multilayer interlocked microdome geometry. Due to the stress concentration between interlocked microdome arrays and increased contact area in the multilayer design, the flexible ferroelectric sensors could perceive static/dynamic pressure with high sensitivity (47.7 kPa -1 , 1.3 Pa minimum detection). In addition, efficient stress distribution between stacked multilayers enables linear sensing over exceptionally broad pressure range (0.0013-353 kPa) with fast response time (20 ms) and high reliability over 5000 repetitive cycles even at an extremely high pressure of 272 kPa. Our sensor can be used to monitor diverse stimuli from a low to a high pressure range including weak gas flow, acoustic sound, wrist pulse pressure, respiration, and foot pressure with a single device.

A Lateral Differential Resonant Pressure Microsensor Based on SOI-Glass Wafer-Level Vacuum Packaging.

PubMed

Xie, Bo; Xing, Yonghao; Wang, Yanshuang; Chen, Jian; Chen, Deyong; Wang, Junbo

2015-09-21

This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device layer as a differential setup. The resonators were vacuum packaged with a glass cap using anodic bonding and the wire interconnection was realized using a mask-free electrochemical etching approach by selectively patterning an Au film on highly topographic surfaces. The fabricated resonant pressure microsensor with dual resonators was characterized in a systematic manner, producing a quality factor higher than 10,000 (~6 months), a sensitivity of about 166 Hz/kPa and a reduced nonlinear error of 0.033% F.S. Based on the differential output, the sensitivity was increased to two times and the temperature-caused frequency drift was decreased to 25%.

Plantar pressure cartography reconstruction from 3 sensors.

PubMed

Abou Ghaida, Hussein; Mottet, Serge; Goujon, Jean-Marc

2014-01-01

Foot problem diagnosis is often made by using pressure mapping systems, unfortunately located and used in the laboratories. In the context of e-health and telemedicine for home monitoring of patients having foot problems, our focus is to present an acceptable system for daily use. We developed an ambulatory instrumented insole using 3 pressures sensors to visualize plantar pressure cartographies. We show that a standard insole with fixed sensor position could be used for different foot sizes. The results show an average error measured at each pixel of 0.01 daN, with a standard deviation of 0.005 daN.

[Intracranial pressure monitoring apparatus for clinical use balanced pressure sensors].

PubMed

Numoto, M

1976-04-01

Three types of pressure sensors, (1) electric pressure switch, (2) fiber optic pressure switch and (3) pressure indicating bag for intracranial pressure monitoring which were developed by the author are described. Advantages and disadvantages between them are also discussed. The electric pressure switch is relatively simple in construction but has a possibility of producing micro-shock hazard in case of accidental electric leakage. The fiber optic pressure switch is the safest for the micro shock but its structure is rather complicated and fragile. The pressure indicating bag is simple to make and durable to use. However, it has a hydrostatic effect.

Central arterial pressure assessment with intensity POF sensor

NASA Astrophysics Data System (ADS)

Leitão, Cátia; Gonçalves, Steve; Antunes, Paulo; Bastos, José M.; Pinto, João. L.; André, Paulo

2015-09-01

The central pressure monitoring is considered a new key factor in hypertension assessment and cardiovascular prevention. In this work, it is presented the central arterial systolic pressure assessment with an intensity based POF sensor. The device was tested in four subjects, and stable pulse waves were obtained, allowing the calculation of the central pressure for all the subjects. The results shown that the sensor performs reliably, being a simple and low-cost solution to the intended application.

Vibration modes interference in the MEMS resonant pressure sensor

NASA Astrophysics Data System (ADS)

Zhang, Fangfang; Li, Anlin; Bu, Zhenxiang; Wang, Lingyun; Sun, Daoheng; Du, Xiaohui; Gu, Dandan

2017-11-01

A new type of coupled balanced-mass double-ended tuning fork resonator (CBDETF) pressure sensor is fabricated and tested. However, the low accuracy of the CBDETF pressure sensor is not satisfied to us. Based on systematic analysis and tests, the coupling effect between the operational mode and interference mode is considered to be the main cause for the sensor in accuracy. To solve this problem, the stiffness of the serpentine beams is increased to pull up the resonant frequency of the interfering mode and make it separate far from the operational mode. Finally, the accuracy of the CBDETF pressure sensor is improved from + /-0.5% to less than + /-0.03% of the Full Scale (F.S.).

Low-Cost Fiber Optic Pressure Sensor

DOEpatents

Sheem, Sang K.

2004-05-18

The size and cost of fabricating fiber optic pressure sensors is reduced by fabricating the membrane of the sensor in a non-planar shape. The design of the sensors may be made in such a way that the non-planar membrane becomes a part of an air-tight cavity, so as to make the membrane resilient due to the air-cushion effect of the air-tight cavity. Such non-planar membranes are easier to make and attach.

Low-Cost Fiber Optic Pressure Sensor

DOEpatents

Sheem, Sang K.

2003-07-22

The size and cost of fabricating fiber optic pressure sensors is reduced by fabricating the membrane of the sensor in a non-planar shape. The design of the sensors may be made in such a way that the non-planar membrane becomes a part of an air-tight cavity, so as to make the membrane resilient due to the air-cushion effect of the air-tight cavity. Such non-planar membranes are easier to make and attach.

Simple, reliable, and nondestructive method for the measurement of vacuum pressure without specialized equipment.

PubMed

Yuan, Jin-Peng; Ji, Zhong-Hua; Zhao, Yan-Ting; Chang, Xue-Fang; Xiao, Lian-Tuan; Jia, Suo-Tang

2013-09-01

We present a simple, reliable, and nondestructive method for the measurement of vacuum pressure in a magneto-optical trap. The vacuum pressure is verified to be proportional to the collision rate constant between cold atoms and the background gas with a coefficient k, which can be calculated by means of the simple ideal gas law. The rate constant for loss due to collisions with all background gases can be derived from the total collision loss rate by a series of loading curves of cold atoms under different trapping laser intensities. The presented method is also applicable for other cold atomic systems and meets the miniaturization requirement of commercial applications.

Operation tools with dielectric elastomer pressure sensors

NASA Astrophysics Data System (ADS)

Böse, Holger; Müller, Dominik; Ehrlich, Johannes

2017-04-01

New sensors based on dielectric elastomers have recently been shown to exhibit high sensitivity for compression loads. The basic design of these sensors exhibits two profiled surfaces coated with electrode layers between which an elastomer film with the counter-electrode is confined. All components of the sensor are prepared with silicone whose stiffness can be varied in a wide range. Depending on the details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression, the elastomer profiles are deformed and the electrode layers on the elastomer profiles and in the elastomer film approach each other. Beside the detection of pressure, such sensors can also be used for operation tools in human-machine interfaces. To demonstrate this potential, a touch pad with six pressure-sensitive fields is presented. The corresponding sensors integrated in the touch fields detect the exerted forces of the finger, show them on a display and control the brightness of some LEDs. As a second example, the integration of sensor-based control fields on an automotive steering wheel is shown. Finally, the sensors can also be used in fabrics to control arbitrary functions of wearable electronic devices.

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.

A miniature 48-channel pressure sensor module capable of in situ calibration

NASA Technical Reports Server (NTRS)

Gross, C.; Juanarena, D. B.

1977-01-01

A new high data rate pressure sensor module with in situ calibration capability has been developed by the Langley Research Center to help reduce energy consumption in wind-tunnel facilities without loss of measurement accuracy. The sensor module allows for nearly a two order of magnitude increase in data rates over conventional electromechanically scanned pressure sampling techniques. This module consists of 16 solid state pressure sensor chips and signal multiplexing electronics integrally mounted to a four position pressure selector switch. One of the four positions of the pressure selector switch allows the in situ calibration of the 16 pressure sensors; the three other positions allow 48 channels (three sets of 16) pressure inputs to be measured by sensors. The small size of the sensor module will allow mounting within many wind-tunnel models, thus eliminating long tube lengths and their corresponding slow pressure response.

Suppression of span in sealed microcavity Fabry-Perot pressure sensors

NASA Astrophysics Data System (ADS)

Mishra, Shivam; Rajappa, Balasubramaniam; Chandra, Sudhir

2017-01-01

Optical microelectromechanical system pressure sensors working on the principle of extrinsic Fabry-Perot (FP) interferometer are designed and fabricated for pressure range of 1-bar absolute. Anodic bonding of silicon with glass is performed under atmospheric pressure to form FP cavity. This process results in entrapment of gas in the sealed microcavity. The effect of trapped gas is investigated on sensor characteristics. A closed-loop solution is derived for the deflection of the diaphragm of a sealed microcavity pressure sensor. Phenomenon of "suppression of span" is brought out. The sensors are tested using white light interferometry technique. The residual pressure of the trapped gas is estimated from the experiments. The developed model has been used to estimate the deflection sensitivity of the free diaphragm and the extent of suppression of span after bonding.

Recent Improvement of Medical Optical Fibre Pressure and Temperature Sensors.

PubMed

Poeggel, Sven; Duraibabu, Dineshbabu; Kalli, Kyriacos; Leen, Gabriel; Dooly, Gerard; Lewis, Elfed; Kelly, Jimmy; Munroe, Maria

2015-07-13

This investigation describes a detailed analysis of the fabrication and testing of optical fibre pressure and temperature sensors (OFPTS). The optical sensor of this research is based on an extrinsic Fabry-Perot interferometer (EFPI) with integrated fibre Bragg grating (FBG) for simultaneous pressure and temperature measurements. The sensor is fabricated exclusively in glass and with a small diameter of 0.2 mm, making it suitable for volume-restricted bio-medical applications. Diaphragm shrinking techniques based on polishing, hydrofluoric (HF) acid and femtosecond (FS) laser micro-machining are described and analysed. The presented sensors were examined carefully and demonstrated a pressure sensitivity in the range of sp = 2-10 nm/kPa and a resolution of better than ΔP = 10 Pa protect (0.1 cm H2O). A static pressure test in 38 cm H2O shows no drift of the sensor in a six-day period. Additionally, a dynamic pressure analysis demonstrated that the OFPTS never exceeded a drift of more than 130 Pa (1.3 cm H2O) in a 12-h measurement, carried out in a cardiovascular simulator. The temperature sensitivity is given by k = 10.7 pm/K, which results in a temperature resolution of better than ΔT = 0.1 K. Since the temperature sensing element is placed close to the pressure sensing element, the pressure sensor is insensitive to temperature changes.

Recent Improvement of Medical Optical Fibre Pressure and Temperature Sensors

PubMed Central

Poeggel, Sven; Duraibabu, Dineshbabu; Kalli, Kyriacos; Leen, Gabriel; Dooly, Gerard; Lewis, Elfed; Kelly, Jimmy; Munroe, Maria

2015-01-01

This investigation describes a detailed analysis of the fabrication and testing of optical fibre pressure and temperature sensors (OFPTS). The optical sensor of this research is based on an extrinsic Fabry–Perot interferometer (EFPI) with integrated fibre Bragg grating (FBG) for simultaneous pressure and temperature measurements. The sensor is fabricated exclusively in glass and with a small diameter of 0.2 mm, making it suitable for volume-restricted bio-medical applications. Diaphragm shrinking techniques based on polishing, hydrofluoric (HF) acid and femtosecond (FS) laser micro-machining are described and analysed. The presented sensors were examined carefully and demonstrated a pressure sensitivity in the range of sp = 2–10 nmkPa and a resolution of better than ΔP = 10 Pa (0.1 cm H2O). A static pressure test in 38 cmH2O shows no drift of the sensor in a six-day period. Additionally, a dynamic pressure analysis demonstrated that the OFPTS never exceeded a drift of more than 130 Pa (1.3 cm H2O) in a 12-h measurement, carried out in a cardiovascular simulator. The temperature sensitivity is given by k=10.7 pmK, which results in a temperature resolution of better than ΔT = 0.1 K. Since the temperature sensing element is placed close to the pressure sensing element, the pressure sensor is insensitive to temperature changes. PMID:26184331

A Lateral Differential Resonant Pressure Microsensor Based on SOI-Glass Wafer-Level Vacuum Packaging

PubMed Central

Xie, Bo; Xing, Yonghao; Wang, Yanshuang; Chen, Jian; Chen, Deyong; Wang, Junbo

2015-01-01

This paper presents the fabrication and characterization of a resonant pressure microsensor based on SOI-glass wafer-level vacuum packaging. The SOI-based pressure microsensor consists of a pressure-sensitive diaphragm at the handle layer and two lateral resonators (electrostatic excitation and capacitive detection) on the device layer as a differential setup. The resonators were vacuum packaged with a glass cap using anodic bonding and the wire interconnection was realized using a mask-free electrochemical etching approach by selectively patterning an Au film on highly topographic surfaces. The fabricated resonant pressure microsensor with dual resonators was characterized in a systematic manner, producing a quality factor higher than 10,000 (~6 months), a sensitivity of about 166 Hz/kPa and a reduced nonlinear error of 0.033% F.S. Based on the differential output, the sensitivity was increased to two times and the temperature-caused frequency drift was decreased to 25%. PMID:26402679

Self-Correcting Electronically-Scanned Pressure Sensor

NASA Technical Reports Server (NTRS)

Gross, C.; Basta, T.

1982-01-01

High-data-rate sensor automatically corrects for temperature variations. Multichannel, self-correcting pressure sensor can be used in wind tunnels, aircraft, process controllers and automobiles. Offers data rates approaching 100,000 measurements per second with inaccuracies due to temperature shifts held below 0.25 percent (nominal) of full scale over a temperature span of 55 degrees C.

Comparison of actual vacuum pressures at the end of 3 phacoemulsification tips in swine eyes.

PubMed

Park, Sang Hoon; Choi, Chul Young; Kim, Joon Mo; Chang, Hae Ran; Kim, Jae Yong; Kim, Myoung Joon; Tchah, Hungwon; Kim, Jae Chan

2009-05-01

To compare the actual vacuum pressure at the end of an aspiration bypass system (ABS) phaco tip and a conventional tip in conditions similar to those during human cataract surgery. Kangbuk Samsung Hospital, Seoul, Korea. A 4.0 mm diameter rubber eraser ball was inserted in a phacoemulsified swine eye and engaged to a phaco tip. With a vacuum pressure of 300 mm Hg, the eraser ball was pulled in the opposite direction with the phaco tip. The pulling power separating the eraser ball from the phaco tip was measured using the volume of water dripped into a container connected to the eraser ball. Measurements were taken with an Infiniti ABS tip and 2 conventional tips: Sovereign (conventional tip S) and Infiniti (conventional tip I). Measurements were taken alternatively at random in the same eye. The mean pulling power was 17.35 mL +/- 5.01 (SD) with conventional tip S and 16.85 +/- 4.45 mL with conventional tip I. The mean pulling power of the ABS tip was 13.35 +/- 4.32 mL, which was a mean 20.8% lower than that of conventional tip I (P = .016) and 23.1% lower than that of conventional tip S (P = .010). The actual vacuum pressure of the phaco tip was significantly influenced by the presence of the ABS hole. To compensate for the decrease in actual vacuum pressure, surgeons should be aware of the characteristics of the ABS tip being used and change the standard settings accordingly.

Remote vacuum or pressure sealing device and method for critical isolated systems

DOEpatents

Brock, James David [Newport News, VA; Keith, Christopher D [Newport News, VA

2012-07-10

A remote vacuum or pressure sealing apparatus and method for making a radiation tolerant, remotely prepared seal that maintains a vacuum or pressure tight seal throughout a wide temperature range. The remote sealing apparatus includes a fixed threaded sealing surface on an isolated system, a gasket, and an insert consisting of a plug with a protruding sample holder. An insert coupling device, provided for inserting samples within the isolated system, includes a threaded fastener for cooperating with the fixed threaded sealing surface on the isolated system. The insert coupling device includes a locating pin for azimuthal orientation, coupling pins, a tooted coaxial socket wrench, and an insert coupling actuator for actuating the coupling pins. The remote aspect of the sealing apparatus maintains the isolation of the system from the user's environment, safely preserving the user and the system from detrimental effect from each respectively.

Analysis on the impact of FBG reflectance spectrum with different optical fiber connection in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Zhang, Jingchuan; Zhang, Wen; Lv, Jianfeng; Liang, Shuo; Wang, Lei; Li, Xiyuan

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, FBG on sleeve compactly single model fiber with two typical different kind of connection such as fiber splicing and optical fiber connector are researched. Influence of the different connection to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, experimental program of influence on FBG reflection spectrum characteristics is designed. Then, a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG with two typical different connections under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different single-mode optical fiber connection dropped to -196 °C from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 °C temperature cycle).

Effects of ambient temperature and water vapor on chamber pressure and oxygen level during low atmospheric pressure stunning of poultry

PubMed Central

Holloway, Paul H.; Pritchard, David G.

2017-01-01

Abstract The characteristics of the vacuum used in a low atmospheric pressure stunning system to stun (render unconscious) poultry prior to slaughter are described. A vacuum chamber is pumped by a wet screw compressor. The vacuum pressure is reduced from ambient atmospheric pressure to an absolute vacuum pressure of ∼250 Torr (∼33 kPa) in ∼67 sec with the vacuum gate valve fully open. At ∼250 Torr, the sliding gate valve is partially closed to reduce effective pumping speed, resulting in a slower rate of decreasing pressure. Ambient temperature affects air density and water vapor pressure and thereby oxygen levels and the time at the minimum total pressure of ∼160 Torr (∼21 kPa) is varied from ∼120 to ∼220 sec to ensure an effective stun within the 280 seconds of each cycle. The reduction in total pressure results in a gradual reduction of oxygen partial pressure that was measured by a solid-state electrochemical oxygen sensor. The reduced oxygen pressure leads to hypoxia, which is recognized as a humane method of stunning poultry. The system maintains an oxygen concentration of <5% for at least 2 minutes, which ensures that birds are irreversibly stunned. Calculated pump down (pressure versus time) data match experimental data very closely because the programmable logic controller and the human machine interface enable precise and accurate control. The vacuum system operates in the turbulent viscous flow regime, and is best characterized by absolute vacuum pressure rather than gauge pressure. Neither the presence of broiler chickens nor different fore-line pipe designs of four parallel commercial systems affected the pressure-time data. Water in wet air always reduces the oxygen concentrations to a value lower than in dry air. The partial pressure of water and oxygen were found to depend on the pump down parameters due to the formation of fog in the chamber and desorption of water from the birds and the walls of the vacuum chamber. PMID

Ultrafast Dynamic Pressure Sensors Based on Graphene Hybrid Structure.

PubMed

Liu, Shanbiao; Wu, Xing; Zhang, Dongdong; Guo, Congwei; Wang, Peng; Hu, Weida; Li, Xinming; Zhou, Xiaofeng; Xu, Hejun; Luo, Chen; Zhang, Jian; Chu, Junhao

2017-07-19

Mechanical flexible electronic skin has been focused on sensing various physical parameters, such as pressure and temperature. The studies of material design and array-accessible devices are the building blocks of strain sensors for subtle pressure sensing. Here, we report a new and facile preparation of a graphene hybrid structure with an ultrafast dynamic pressure response. Graphene oxide nanosheets are used as a surfactant to prevent graphene restacking in aqueous solution. This graphene hybrid structure exhibits a frequency-independent pressure resistive sensing property. Exceeding natural skin, such pressure sensors, can provide transient responses from static up to 10 000 Hz dynamic frequencies. Integrated by the controlling system, the array-accessible sensors can manipulate a robot arm and self-rectify the temperature of a heating blanket. This may pave a path toward the future application of graphene-based wearable electronics.

Ultrasonic level sensors for liquids under high pressure

NASA Technical Reports Server (NTRS)

Zuckerwar, A. J.; Mazel, D. S.; Hodges, D. Y.

1986-01-01

An ultrasonic level sensor of novel design continuously measures the level of a liquid subjected to a high pressure (up to about 40 MPa), as is sometimes required for the effective transfer of the liquid. The sensor operates as a composite resonator fabricated from a standard high-pressure plug. A flat-bottom hole is machined into the plug along its center line. An ultrasonic transducer is bonded rigidly to the interior surface of the bottom wall, while the exterior surface is in contact with the liquid. Although the bottom wall is designed to satisfy the pressure code, it is still sufficiently thin to permit ready excitation of the axisymmetric plate modes of vibration. The liquid level is measured by a conventional pulse-echo technique. A prototype sensor was tested successfully in a 2300-l water vessel at pressures up to about 37 MPa. A spectral analysis of the transmitted pulse reveals that the flexural, extensional, thickness-shear, and radial plate modes are excited into vibration, but none of these appears to be significantly affected by the pressurization of the liquid.

Capacitive Micro Pressure Sensor Integrated with a Ring Oscillator Circuit on Chip

PubMed Central

Dai, Ching-Liang; Lu, Po-Wei; Chang, Chienliu; Liu, Cheng-Yang

2009-01-01

The study investigates a capacitive micro pressure sensor integrated with a ring oscillator circuit on a chip. The integrated capacitive pressure sensor is fabricated using the commercial CMOS (complementary metal oxide semiconductor) process and a post-process. The ring oscillator is employed to convert the capacitance of the pressure sensor into the frequency output. The pressure sensor consists of 16 sensing cells in parallel. Each sensing cell contains a top electrode and a lower electrode, and the top electrode is a sandwich membrane. The pressure sensor needs a post-CMOS process to release the membranes after completion of the CMOS process. The post-process uses etchants to etch the sacrificial layers, and to release the membranes. The advantages of the post-process include easy execution and low cost. Experimental results reveal that the pressure sensor has a high sensitivity of 7 Hz/Pa in the pressure range of 0–300 kPa. PMID:22303167

Capacitive micro pressure sensor integrated with a ring oscillator circuit on chip.

PubMed

Dai, Ching-Liang; Lu, Po-Wei; Chang, Chienliu; Liu, Cheng-Yang

2009-01-01

The study investigates a capacitive micro pressure sensor integrated with a ring oscillator circuit on a chip. The integrated capacitive pressure sensor is fabricated using the commercial CMOS (complementary metal oxide semiconductor) process and a post-process. The ring oscillator is employed to convert the capacitance of the pressure sensor into the frequency output. The pressure sensor consists of 16 sensing cells in parallel. Each sensing cell contains a top electrode and a lower electrode, and the top electrode is a sandwich membrane. The pressure sensor needs a post-CMOS process to release the membranes after completion of the CMOS process. The post-process uses etchants to etch the sacrificial layers, and to release the membranes. The advantages of the post-process include easy execution and low cost. Experimental results reveal that the pressure sensor has a high sensitivity of 7 Hz/Pa in the pressure range of 0-300 kPa.

Development of a directional sensitive pressure and shear sensor

NASA Astrophysics Data System (ADS)

Wang, Wei-Chih; Dee, Jeffrey; Ledoux, William; Sangeorzan, Bruce; Reinhall, Per G.

2002-06-01

Diabetes mellitus is a disease that impacts the lives of millions of people around the world. Lower limb complications associated with diabetes include the development of plantar ulcers that can lead to infection and subsequent amputation. Shear stress is thought to be a major contributing factor to ulcer development, but due in part to technical difficulties with transducing shear stress, there is no widely used shear measurement sensor. As such, we are currently developing a directionally sensitive pressure/shear sensor based on fiber optic technology. The pressure/shear sensor consists of an array of optical fibers lying in perpendicular rows and columns separated by elastomeric pads. A map of pressure and shear stress is constructed based on observed macro bending through the intensity attenuation from the physical deformation of two adjacent perpendicular fibers. The sensor has been shown to have low noise and responded linearly to applied loads. The smallest detectable force on each sensor element based on the current setup is ~0.1 lbs. (0.4N). The smallest area we have resolved in our mesh sensor is currently ~1 cm2.

Device for determining carbon activity through pressure

DOEpatents

Roche, Michael F.

1976-01-01

A hollow iron capsule of annular shape having an interior layer of Fe.sub.0.947 0 and a near absolute internal vacuum is submersed within a molten metal with the inner chamber of the capsule connected to a pressure sensor. Carbon present in the molten metal diffuses through the capsule wall and reacts with the Fe.sub.0.947 0 layer to generate a CO.sub.2 --CO gas mixture within the internal chamber. The total absolute pressure of the gas measured by the pressure sensor is directly proportional to the carbon activity of the molten metal.

An ultra-fast fiber optic pressure sensor for blast event measurements

NASA Astrophysics Data System (ADS)

Wu, Nan; Zou, Xiaotian; Tian, Ye; Fitek, John; Maffeo, Michael; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

2012-05-01

Soldiers who are exposed to explosions are at risk of suffering traumatic brain injury (TBI). Since the causal relationship between a blast and TBI is poorly understood, it is critical to have sensors that can accurately quantify the blast dynamics and resulting wave propagation through a helmet and skull that are imparted onto and inside the brain. To help quantify the cause of TBI, it is important to record transient pressure data during a blast event. However, very few sensors feature the capabilities of tracking the dynamic pressure transients due to the rapid change of the pressure during blast events, while not interfering with the physical material layers or wave propagation. In order to measure the pressure transients efficiently, a pressure sensor should have a high resonant frequency and a high spatial resolution. This paper describes an ultra-fast fiber optic pressure sensor based on the Fabry-Perot principle for the application of measuring the rapid pressure changes in a blast event. A shock tube experiment performed in US Army Natick Soldier Research, Development and Engineering Center has demonstrated that the resonant frequency of the sensor is 4.12 MHz, which is relatively close to the designed theoretical value of 4.113 MHz. Moreover, the experiment illustrated that the sensor has a rise time of 120 ns, which demonstrates that the sensor is capable of observing the dynamics of the pressure transient during a blast event.

Inductive passive sensor for intraparenchymal and intraventricular monitoring of intracranial pressure.

PubMed

Behfar, Mohammad H; Abada, Emily; Sydanheimo, Lauri; Goldman, Ken; Fleischman, Aaron J; Gupta, Nalin; Ukkonen, Leena; Roy, Shuvo

2016-08-01

Accurate measurement of intracranial hypertension is crucial for the management of elevated intracranial pressure (ICP). Catheter-based intraventricular ICP measurement is regarded as the gold standard for accurate ICP monitoring. However, this method is invasive, time-limited, and associated with complications. In this paper, we propose an implantable passive sensor that could be used for continuous intraparenchymal and intraventricular ICP monitoring. Moreover, the sensor can be placed simultaneously along with a cerebrospinal fluid shunt system in order to monitor its function. The sensor consists of a flexible coil which is connected to a miniature pressure sensor via an 8-cm long, ultra-thin coaxial cable. An external orthogonal-coil RF probe communicates with the sensor to detect pressure variation. The performance of the sensor was evaluated in an in vitro model for intraparenchymal and intraventricular ICP monitoring. The findings from this study demonstrate proof-of-concept of intraparenchymal and intraventricular ICP measurement using inductive passive pressure sensors.

Electrospray-printed nanostructured graphene oxide gas sensors

NASA Astrophysics Data System (ADS)

Taylor, Anthony P.; Velásquez-García, Luis F.

2015-12-01

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.

Research on influence of different cover to the characteristic of FBG reflectance spectrum in vacuum thermal environment

NASA Astrophysics Data System (ADS)

Pei, Yifei; Zhang, Jingchuan; Zhang, Luosha; Liu, Yang; Zhang, Lina; Chen, Shiyu

2018-01-01

To satisfy the application of fiber grating sensor technology in high vacuum thermal environment, two different kinds of sleeve compactly single model fiber covered by acrylate and polyimide are researched. Influence of the cover to the characteristic of FBG reflectance spectrum in high vacuum thermal environment is analyzed and verified. First, transmission characteristic of single model fiber in high vacuum thermal environment is analyzed by solve the equation of heat conduction. Then, experimental program of influence on FBG reflection spectrum characteristics is designed and a hardware-in-the-loop detection platform is set up. Finally, the influence of temperature and vacuum on the reflection peak power of FBG in different coating single-mode transmission fiber under high vacuum thermal environment is studied and verified. Experimental results indicate that: when vacuum varied from normal pressure to 10-4Pa level and then return to normal pressure, temperature of two different coating single-mode transmission fiber dropped to -196 ° from room temperature and then returned to room temperature, after 224 hours, the peak power of the FBG reflectance spectrum did not change. It provided the theoretical and experimental basis for the application of optical fiber sensing technology in high vacuum (pressure about 10-4Pa level) and thermal environment (-196 ° 25 ° temperature cycle) .

Tunable-Sensitivity flexible pressure sensor based on graphene transparent electrode

NASA Astrophysics Data System (ADS)

Luo, Shi; Yang, Jun; Song, Xuefen; Zhou, Xi; Yu, Leyong; Sun, Tai; Yu, Chongsheng; Huang, Deping; Du, Chunlei; Wei, Dapeng

2018-07-01

Tunable-sensitivity and flexibility are considered as two crucial characteristics for future pressure sensors or electronic skins. By the theoretical calculation model, we simulated the relationship curve between the sensitivity and PDMS pyramids with different spacings, and found that the spacing of pyramids is a main factor to affect the sensitivity of the capacitance pressure sensor. Furthermore, we fabricated the capacitance pressure sensors using graphene electrodes and the PDMS pyramid dielectric layers with different spacings. The measurement data were consistent with the simulation results that the sensitivity increases with the spacing of pyramids. In addition, graphene electrode exhibits prefect flexibility and reliability, while the ITO electrode would be destroyed rapidly after bending. These graphene pressure sensors exhibit the potential in the application in the wearable products for monitoring breath, pulse, and other physiological signals.

A CMOS Pressure Sensor Tag Chip for Passive Wireless Applications

PubMed Central

Deng, Fangming; He, Yigang; Li, Bing; Zuo, Lei; Wu, Xiang; Fu, Zhihui

2015-01-01

This paper presents a novel monolithic pressure sensor tag for passive wireless applications. The proposed pressure sensor tag is based on an ultra-high frequency RFID system. The pressure sensor element is implemented in the 0.18 µm CMOS process and the membrane gap is formed by sacrificial layer release, resulting in a sensitivity of 1.2 fF/kPa within the range from 0 to 600 kPa. A three-stage rectifier adopts a chain of auxiliary floating rectifier cells to boost the gate voltage of the switching transistors, resulting in a power conversion efficiency of 53% at the low input power of −20 dBm. The capacitive sensor interface, using phase-locked loop archietcture, employs fully-digital blocks, which results in a 7.4 bits resolution and 0.8 µW power dissipation at 0.8 V supply voltage. The proposed passive wireless pressure sensor tag costs a total 3.2 µW power dissipation. PMID:25806868

A CMOS pressure sensor tag chip for passive wireless applications.

PubMed

Deng, Fangming; He, Yigang; Li, Bing; Zuo, Lei; Wu, Xiang; Fu, Zhihui

2015-03-23

This paper presents a novel monolithic pressure sensor tag for passive wireless applications. The proposed pressure sensor tag is based on an ultra-high frequency RFID system. The pressure sensor element is implemented in the 0.18 µm CMOS process and the membrane gap is formed by sacrificial layer release, resulting in a sensitivity of 1.2 fF/kPa within the range from 0 to 600 kPa. A three-stage rectifier adopts a chain of auxiliary floating rectifier cells to boost the gate voltage of the switching transistors, resulting in a power conversion efficiency of 53% at the low input power of -20 dBm. The capacitive sensor interface, using phase-locked loop archietcture, employs fully-digital blocks, which results in a 7.4 bits resolution and 0.8 µW power dissipation at 0.8 V supply voltage. The proposed passive wireless pressure sensor tag costs a total 3.2 µW power dissipation.

Temperature Compensation Fiber Bragg Grating Pressure Sensor Based on Plane Diaphragm

NASA Astrophysics Data System (ADS)

Liang, Minfu; Fang, Xinqiu; Ning, Yaosheng

2018-06-01

Pressure sensors are the essential equipments in the field of pressure measurement. In this work, we propose a temperature compensation fiber Bragg grating (FBG) pressure sensor based on the plane diaphragm. The plane diaphragm and pressure sensitivity FBG (PS FBG) are used as the pressure sensitive components, and the temperature compensation FBG (TC FBG) is used to improve the temperature cross-sensitivity. Mechanical deformation model and deformation characteristics simulation analysis of the diaphragm are presented. The measurement principle and theoretical analysis of the mathematical relationship between the FBG central wavelength shift and pressure of the sensor are introduced. The sensitivity and measure range can be adjusted by utilizing the different materials and sizes of the diaphragm to accommodate different measure environments. The performance experiments are carried out, and the results indicate that the pressure sensitivity of the sensor is 35.7 pm/MPa in a range from 0 MPa to 50 MPa and has good linearity with a linear fitting correlation coefficient of 99.95%. In addition, the sensor has the advantages of low frequency chirp and high stability, which can be used to measure pressure in mining engineering, civil engineering, or other complex environment.

Transparent, Flexible, Conformal Capacitive Pressure Sensors with Nanoparticles.

PubMed

Kim, Hyeohn; Kim, Gwangmook; Kim, Taehoon; Lee, Sangwoo; Kang, Donyoung; Hwang, Min-Soo; Chae, Youngcheol; Kang, Shinill; Lee, Hyungsuk; Park, Hong-Gyu; Shim, Wooyoung

2018-02-01

The fundamental challenge in designing transparent pressure sensors is the ideal combination of high optical transparency and high pressure sensitivity. Satisfying these competing demands is commonly achieved by a compromise between the transparency and usage of a patterned dielectric surface, which increases pressure sensitivity, but decreases transparency. Herein, a design strategy for fabricating high-transparency and high-sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. We utilize two nanoparticle dispersion states on a surface: (i) homogeneous dispersion, where each nanoparticle (≈500 nm) with a size comparable to the visible light wavelength has low light scattering; and (ii) heterogeneous dispersion, where aggregated nanoparticles form a micrometer-sized feature, increasing pressure sensitivity. This approach is experimentally verified using a nanoparticle-dispersed polymer composite, which has high pressure sensitivity (1.0 kPa -1 ), and demonstrates excellent transparency (>95%). We demonstrate that the integration of nanoparticle-dispersed capacitor elements into an array readily yields a real-time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor-based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxygen partial pressure sensor

DOEpatents

Dees, D.W.

1994-09-06

A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured. 1 fig.

Oxygen partial pressure sensor

DOEpatents

Dees, Dennis W.

1994-01-01

A method for detecting oxygen partial pressure and an oxygen partial pressure sensor are provided. The method for measuring oxygen partial pressure includes contacting oxygen to a solid oxide electrolyte and measuring the subsequent change in electrical conductivity of the solid oxide electrolyte. A solid oxide electrolyte is utilized that contacts both a porous electrode and a nonporous electrode. The electrical conductivity of the solid oxide electrolyte is affected when oxygen from an exhaust stream permeates through the porous electrode to establish an equilibrium of oxygen anions in the electrolyte, thereby displacing electrons throughout the electrolyte to form an electron gradient. By adapting the two electrodes to sense a voltage potential between them, the change in electrolyte conductivity due to oxygen presence can be measured.

Development of microbend sensors for pressure, load, and displacement measurements in civil engineering

NASA Astrophysics Data System (ADS)

Grossman, Barry G.; Cosentino, Paul J.; Doi, Shinobu; Kumar, Girish; Verghese, John

1994-05-01

We are developing low cost, rugged, and reliable fiberoptic sensors to meet current and future needs in civil engineering, including those of smart civil structures. Our work has concentrated on load, pressure, and displacement sensors, including pore water pressure sensors. We have built and demonstrated sensors in the laboratory with loads up to 50 lb., water pressures of 100 psi, and displacements up to 1 mm. Repeatability of sensor measurements are within 5% and are being improved with continued development. The range and sensitivity of the sensors can be easily changed without changing the basic sensor design. We also have multiplexed two water pressure sensors on a single fiber. We describe the sensor construction and experimental performance.

Piezoelectric power generation for sensor applications: design of a battery-less wireless tire pressure sensor

NASA Astrophysics Data System (ADS)

Makki, Noaman; Pop-Iliev, Remon

2011-06-01

An in-wheel wireless and battery-less piezo-powered tire pressure sensor is developed. Where conventional battery powered Tire Pressure Monitoring Systems (TPMS) are marred by the limited battery life, TPMS based on power harvesting modules provide virtually unlimited sensor life. Furthermore, the elimination of a permanent energy reservoir simplifies the overall sensor design through the exclusion of extra circuitry required to sense vehicle motion and conserve precious battery capacity during vehicle idling periods. In this paper, two design solutions are presented, 1) with very low cost highly flexible piezoceramic (PZT) bender elements bonded directly to the tire to generate power required to run the sensor and, 2) a novel rim mounted PZT harvesting unit that can be used to power pressure sensors incorporated into the valve stem requiring minimal change to the presently used sensors. While both the designs eliminate the use of environmentally unfriendly battery from the TPMS design, they offer advantages of being very low cost, service free and easily replaceable during tire repair and replacement.

Static and cyclic performance evaluation of sensors for human interface pressure measurement.

PubMed

Dabling, Jeffrey G; Filatov, Anton; Wheeler, Jason W

2012-01-01

Researchers and clinicians often desire to monitor pressure distributions on soft tissues at interfaces to mechanical devices such as prosthetics, orthotics or shoes. The most common type of sensor used for this type of applications is a Force Sensitive Resistor (FSR) as these are convenient to use and inexpensive. Several other types of sensors exist that may have superior sensing performance but are less ubiquitous or more expensive, such as optical or capacitive sensors. We tested five sensors (two FSRs, one optical, one capacitive and one fluid pressure) in a static drift and cyclic loading configuration. The results show that relative to the important performance characteristics for soft tissue pressure monitoring (i.e. hysteresis, drift), many of the sensors tested have significant limitations. The FSRs exhibited hysteresis, drift and loss of sensitivity under cyclic loading. The capacitive sensor had substantial drift. The optical sensor had some hysteresis and temperature-related drift. The fluid pressure sensor performed well in these tests but is not as flat as the other sensors and is not commercially available. Researchers and clinicians should carefully consider the convenience and performance trade-offs when choosing a sensor for soft-tissue pressure monitoring.

High-speed pressure clamp.

PubMed

Besch, Stephen R; Suchyna, Thomas; Sachs, Frederick

2002-10-01

We built a high-speed, pneumatic pressure clamp to stimulate patch-clamped membranes mechanically. The key control element is a newly designed differential valve that uses a single, nickel-plated piezoelectric bending element to control both pressure and vacuum. To minimize response time, the valve body was designed with minimum dead volume. The result is improved response time and stability with a threefold decrease in actuation latency. Tight valve clearances minimize the steady-state air flow, permitting us to use small resonant-piston pumps to supply pressure and vacuum. To protect the valve from water contamination in the event of a broken pipette, an optical sensor detects water entering the valve and increases pressure rapidly to clear the system. The open-loop time constant for pressure is 2.5 ms for a 100-mmHg step, and the closed-loop settling time is 500-600 micros. Valve actuation latency is 120 micros. The system performance is illustrated for mechanically induced changes in patch capacitance.

Quasi-adiabatic vacuum-based column housing for very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; Gilar, Martin; Jarrell, Joseph A

2016-07-22

A prototype vacuum-based (10(-6)Torr) column housing was built to thermally isolate the chromatographic column from the external air environment. The heat transfer mechanism is solely controlled by surface radiation, which was minimized by wrapping the column with low-emissivity aluminum tape. The adiabaticity of the column housing was quantitatively assessed from the measurement of the operational pressure and fluid temperature at the outlet of a 2.1mm×100mm column (sub-2 μm particles). The pressure drop along the column was raised up to 1kbar. The enthalpy balance of the eluent (water, acetonitrile, and one water/acetonitrile mixture, 70/30, v/v) showed that less than 1% of the viscous heat generated by friction of the fluid against the packed bed was lost to the external air environment. Such a vacuum-based column oven minimizes the amplitude of the radial temperature gradients across the column diameter and maximizes its resolving power. Copyright © 2016 Elsevier B.V. All rights reserved.

Microfabricated Nickel Based Sensors for Hostile and High Pressure Environments

NASA Astrophysics Data System (ADS)

Holt, Christopher Michael Bjustrom

This thesis outlines the development of two platforms for integrating microfabricated sensors with high pressure feedthroughs for application in hostile high temperature high pressure environments. An application in oil well production logging is explored and two sensors were implemented with these platforms for application in an oil well. The first platform developed involved microfabrication directly onto a cut and polished high pressure feedthrough. This technique enables a system that is more robust than the wire bonded silicon die technique used for MEMS integration in pressure sensors. Removing wire bonds from the traditional MEMS package allows for direct interface of a microfabricated sensor with a hostile high pressure fluid environment which is not currently possible. During the development of this platform key performance metrics included pressure testing to 70MPa and temperature cycling from 20°C to 200°C. This platform enables electronics integration with a variety of microfabricated electrical and thermal based sensors which can be immersed within the oil well environment. The second platform enabled free space fabrication of nickel microfabricated devices onto an array of pins using a thick tin sacrificial layer. This technique allowed microfabrication of metal MEMS that are released by distances of 1cm from their substrate. This method is quite flexible and allows for fabrication to be done on any pin array substrate regardless of surface quality. Being able to place released MEMS sensors directly onto traditional style circuit boards, ceramic circuit boards, electrical connectors, ribbon cables, pin headers, or high pressure feedthroughs greatly improves the variety of possible applications and reduces fabrication costs. These two platforms were then used to fabricate thermal conductivity sensors that showed excellent performance for distinguishing between oil, water, and gas phases. Testing was conducted at various flow rates and performance of

Packaged Capacitive Pressure Sensor System for Aircraft Engine Health Monitoring

NASA Technical Reports Server (NTRS)

Scardelletti, Maximilian C.; Zorman, Christian A.

2016-01-01

This paper describes the development of a packaged silicon carbide (SiC) based MEMS pressure sensor system designed specifically for a conventional turbofan engine. The electronic circuit is based on a Clapp-type oscillator that incorporates a 6H-SiC MESFET, a SiCN MEMS capacitive pressure sensor, titanate MIM capacitors, wirewound inductors, and thick film resistors. The pressure sensor serves as the capacitor in the LC tank circuit, thereby linking pressure to the resonant frequency of the oscillator. The oscillator and DC bias circuitry were fabricated on an alumina substrate and secured inside a metal housing. The packaged sensing system reliably operates at 0 to 350 psi and 25 to 540C. The system has a pressure sensitivity of 6.8 x 10E-2 MHzpsi. The packaged system shows negligible difference in frequency response between 25 and 400C. The fully packaged sensor passed standard benchtop acceptance tests and was evaluated on a flight-worthy engine.

Integration of piezo-capacitive and piezo-electric nanoweb based pressure sensors for imaging of static and dynamic pressure distribution.

PubMed

Jeong, Y J; Oh, T I; Woo, E J; Kim, K J

2017-07-01

Recently, highly flexible and soft pressure distribution imaging sensor is in great demand for tactile sensing, gait analysis, ubiquitous life-care based on activity recognition, and therapeutics. In this study, we integrate the piezo-capacitive and piezo-electric nanowebs with the conductive fabric sheets for detecting static and dynamic pressure distributions on a large sensing area. Electrical impedance tomography (EIT) and electric source imaging are applied for reconstructing pressure distribution images from measured current-voltage data on the boundary of the hybrid fabric sensor. We evaluated the piezo-capacitive nanoweb sensor, piezo-electric nanoweb sensor, and hybrid fabric sensor. The results show the feasibility of static and dynamic pressure distribution imaging from the boundary measurements of the fabric sensors.

Performance of an untethered micro-optical pressure sensor

NASA Astrophysics Data System (ADS)

Ioppolo, Tindaro; Manzo, Maurizio; Krueger, Paul

2012-11-01

We present analytical and computational studies of the performance of a novel untethered micro-optical pressure sensor for fluid dynamics measurements. In particular, resolution and dynamic range will be presented. The sensor concept is based on the whispering galley mode (WGM) shifts that are observed in micro-scale dielectric optical cavities. A micro-spherical optical cavity (liquid or solid) is embedded in a thin polymeric sheet. The applied external pressure perturbs the morphology of the optical cavity leading to a shift in its optical resonances. The optical sensors are interrogated remotely, by embedding quantum dots or fluorescent dye in the micro-optical cavity. This allows a free space coupling of excitation and monitoring of the optical modes without the need of optical fibers or other cabling. With appropriate excitation and monitoring equipment, the micro-scale sensors can be distributed over a surface (e.g., including flexible biological surfaces) to monitor the local pressure field. We acknowledge the financial support from the National Science Foundation through grant CBET-1133876 with Dr. Horst Henning Winter as the program director.

Ultra fast all-optical fiber pressure sensor for blast event evaluation

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Wenhui; Tian, Ye; Niezrecki, Christopher; Wang, Xingwei

2011-05-01

Traumatic brain injury (TBI) is a great potential threat to soldiers who are exposed to explosions or athletes who receive cranial impacts. Protecting people from TBI has recently attracted a significant amount of attention due to recent military operations in the Middle East. Recording pressure transient data in a blast event is very critical to the understanding of the effects of blast events on TBI. However, due to the fast change of the pressure during blast events, very few sensors have the capability to effectively track the dynamic pressure transients. This paper reports an ultra fast, miniature and all-optical fiber pressure sensor which could be mounted at different locations of a helmet to measure the fast changing pressure simultaneously. The sensor is based on Fabry-Perot (FP) principle. The end face of the fiber is wet etched. A well controlled thickness silicon dioxide diaphragm is thermal bonded on the end face to form an FP cavity. A shock tube test was conducted at Natick Soldier Research Development and Engineering Center, where the sensors were mounted in a shock tube side by side with a reference sensor to measure the rapidly changing pressure. The results of the test demonstrated that the sensor developed had an improved rise time (shorter than 0.4 μs) when compared to a commercially available reference sensor.

A minimally invasive in-fiber Bragg grating sensor for intervertebral disc pressure measurements

NASA Astrophysics Data System (ADS)

Dennison, Christopher R.; Wild, Peter M.; Wilson, David R.; Cripton, Peter A.

2008-08-01

We present an in-fiber Bragg grating (FBG) based intervertebral disc (IVD) pressure sensor that has pressure sensitivity seven times greater than that of a bare fiber, and a major diameter and sensing area of only 400 µm and 0.03 mm2, respectively. This is the only optical, the smallest and the most mechanically compliant disc pressure sensor reported in the literature. This is also an improvement over other FBG pressure sensors that achieve increased sensitivity through mechanical amplification schemes, usually resulting in major diameters and sensing lengths of many millimeters. Sensor sensitivity is predicted using numerical models, and the predicted sensitivity is verified through experimental calibrations. The sensor is validated by conducting IVD pressure measurements in porcine discs and comparing the FBG measurements to those obtained using the current standard sensor for IVD pressure. The predicted sensitivity of the FBG sensor matched with that measured experimentally. IVD pressure measurements showed excellent repeatability and agreement with those obtained from the standard sensor. Unlike the current larger sensors, the FBG sensor could be used in discs with small disc height (i.e. cervical or degenerated discs). Therefore, there is potential to conduct new measurements that could lead to new understanding of the biomechanics.

Direct Printing of Stretchable Elastomers for Highly Sensitive Capillary Pressure Sensors.

PubMed

Liu, Wenguang; Yan, Chaoyi

2018-03-28

We demonstrate the successful fabrication of highly sensitive capillary pressure sensors using an innovative 3D printing method. Unlike conventional capacitive pressure sensors where the capacitance changes were due to the pressure-induced interspace variations between the parallel plate electrodes, in our capillary sensors the capacitance was determined by the extrusion and extraction of liquid medium and consequent changes of dielectric constants. Significant pressure sensitivity advances up to 547.9 KPa -1 were achieved. Moreover, we suggest that our innovative capillary pressure sensors can adopt a wide range of liquid mediums, such as ethanol, deionized water, and their mixtures. The devices also showed stable performances upon repeated pressing cycles. The direct and versatile printing method combined with the significant performance advances are expected to find important applications in future stretchable and wearable electronics.

Cantilever arrayed blood pressure sensor for arterial applanation tonometry.

PubMed

Lee, Byeungleul; Jeong, Jinwoo; Kim, Jinseok; Kim, Bonghwan; Chun, Kukjin

2014-03-01

The authors developed a cantilever-arrayed blood pressure sensor array fabricated by (111) silicon bulk-micromachining for the non-invasive and continuous measurement of blood pressure. The blood pressure sensor measures the blood pressure based on the change in the resistance of the piezoresistor on a 5-microm-thick-arrayed perforated membrane and 20-microm-thick metal pads. The length and the width of the unit membrane are 210 and 310 microm, respectively. The width of the insensible zone between the adjacent units is only 10 microm. The resistance change over contact force was measured to verify the performance. The good linearity of the result confirmed that the polydimethylsiloxane package transfers the forces appropriately. The measured sensitivity was about 4.5%/N. The maximum measurement range and the resolution of the fabricated blood pressure sensor were greater than 900 mmHg (= 120 kPa) and less than 1 mmHg (= 133.3 Pa), respectively.

Insulation Technology in Dry Air and Vacuum for a 72kV Low Pressured Dry Air Insulated Switchgear

NASA Astrophysics Data System (ADS)

Yoshida, Tadahiro; Koga, Hiromi; Harada, Takakazu; Miki, Shinichi; Arioka, Masahiro; Sato, Shinji; Yoshida, Satoru; Inoue, Naoaki; Maruyama, Akihiko; Takeuchi, Toshie

A new 72kV rated low pressured dry air insulated switchgear applying electromagnetic actuation and function that supports CBM has been developed. First, dielectric characteristics in dry air under lightning impulse application has been investigated at bare and insulator covered electrodes. Dependence of the breakdown electric field strength on the effective area has been clarified to apply the configuration design of the insulation mold for the vacuum interrupter. In addition, moisture volume dependence on surface resistance has been clarified to decide moisture volume in gas pressure tank. Next, a new vacuum circuit breaker (VCB) has been designed. To keep dimensions from former 72kV SF6 gas insulated switchgear, distance between contacts in vacuum interrupter is needed to be shorter than that of former switchgear. Voltage withstand capability between electrodes practically designed for vacuum interrupter has been investigated under dc voltage application simulated the small capacitive current breaking test. Gap configuration including contacts and slits has been optimized and distance has been shortened 11% from former switchgear. As a result, the new low pressured dry air insulated switchgear has been designed comparably in outer size to former SF6 gas insulated switchgear. Using dry air as an insulation medium with low pressure has been able to reduce the environmental burden.

Vacuum leak detector and method

DOEpatents

Edwards, Jr., David

1983-01-01

Apparatus and method for detecting leakage in a vacuum system involves a moisture trap chamber connected to the vacuum system and to a pressure gauge. Moisture in the trap chamber is captured by freezing or by a moisture adsorbent to reduce the residual water vapor pressure therein to a negligible amount. The pressure gauge is then read to determine whether the vacuum system is leaky. By directing a stream of carbon dioxide or helium at potentially leaky parts of the vacuum system, the apparatus can be used with supplemental means to locate leaks.

Chronically implanted pressure sensors: challenges and state of the field.

PubMed

Yu, Lawrence; Kim, Brian J; Meng, Ellis

2014-10-31

Several conditions and diseases are linked to the elevation or depression of internal pressures from a healthy, normal range, motivating the need for chronic implantable pressure sensors. A simple implantable pressure transduction system consists of a pressure-sensing element with a method to transmit the data to an external unit. The biological environment presents a host of engineering issues that must be considered for long term monitoring. Therefore, the design of such systems must carefully consider interactions between the implanted system and the body, including biocompatibility, surgical placement, and patient comfort. Here we review research developments on implantable sensors for chronic pressure monitoring within the body, focusing on general design requirements for implantable pressure sensors as well as specifications for different medical applications. We also discuss recent efforts to address biocompatibility, efficient telemetry, and drift management, and explore emerging trends.

Chronically Implanted Pressure Sensors: Challenges and State of the Field

PubMed Central

Yu, Lawrence; Kim, Brian J.; Meng, Ellis

2014-01-01

Several conditions and diseases are linked to the elevation or depression of internal pressures from a healthy, normal range, motivating the need for chronic implantable pressure sensors. A simple implantable pressure transduction system consists of a pressure-sensing element with a method to transmit the data to an external unit. The biological environment presents a host of engineering issues that must be considered for long term monitoring. Therefore, the design of such systems must carefully consider interactions between the implanted system and the body, including biocompatibility, surgical placement, and patient comfort. Here we review research developments on implantable sensors for chronic pressure monitoring within the body, focusing on general design requirements for implantable pressure sensors as well as specifications for different medical applications. We also discuss recent efforts to address biocompatibility, efficient telemetry, and drift management, and explore emerging trends. PMID:25365461

A Wireless Pressure Sensor Integrated with a Biodegradable Polymer Stent for Biomedical Applications

PubMed Central

Park, Jongsung; Kim, Ji-Kwan; Patil, Swati J.; Park, Jun-Kyu; Park, SuA; Lee, Dong-Weon

2016-01-01

This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm2 and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent. PMID:27271619

A Wireless Pressure Sensor Integrated with a Biodegradable Polymer Stent for Biomedical Applications.

PubMed

Park, Jongsung; Kim, Ji-Kwan; Patil, Swati J; Park, Jun-Kyu; Park, SuA; Lee, Dong-Weon

2016-06-02

This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm² and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent.

High Resolution and Large Dynamic Range Resonant Pressure Sensor Based on Q-Factor Measurement

NASA Technical Reports Server (NTRS)

Gutierrez, Roman C. (Inventor); Stell, Christopher B. (Inventor); Tang, Tony K. (Inventor); Vorperian, Vatche (Inventor); Wilcox, Jaroslava (Inventor); Shcheglov, Kirill (Inventor); Kaiser, William J. (Inventor)

2000-01-01

A pressure sensor has a high degree of accuracy over a wide range of pressures. Using a pressure sensor relying upon resonant oscillations to determine pressure, a driving circuit drives such a pressure sensor at resonance and tracks resonant frequency and amplitude shifts with changes in pressure. Pressure changes affect the Q-factor of the resonating portion of the pressure sensor. Such Q-factor changes are detected by the driving/sensing circuit which in turn tracks the changes in resonant frequency to maintain the pressure sensor at resonance. Changes in the Q-factor are reflected in changes of amplitude of the resonating pressure sensor. In response, upon sensing the changes in the amplitude, the driving circuit changes the force or strength of the electrostatic driving signal to maintain the resonator at constant amplitude. The amplitude of the driving signals become a direct measure of the changes in pressure as the operating characteristics of the resonator give rise to a linear response curve for the amplitude of the driving signal. Pressure change resolution is on the order of 10(exp -6) torr over a range spanning from 7,600 torr to 10(exp -6) torr. No temperature compensation for the pressure sensor of the present invention is foreseen. Power requirements for the pressure sensor are generally minimal due to the low-loss mechanical design of the resonating pressure sensor and the simple control electronics.

Implantable blood pressure sensor for analyzing elasticity in arteries

NASA Astrophysics Data System (ADS)

Franco-Ayala, Marco; Martínez-Piñón, Fernando; Reyes-Barranca, Alfredo; Sánchez de la Peña, Salvador; Álvarez-Chavez, José A.

2009-03-01

MEMS technology could be an option for the development of a pressure sensor which allows the monitoring of several electronic signals in humans. In this work, a comparison is made between the typical elasticity curves of several arteries in the human body and the elasticity obtained for MEMS silicon microstructures such as membranes and cantilevers employing Finite Element analysis tools. The purpose is to identify which types of microstructures are mechanically compatible with human arteries. The goal is to integrate a blood pressure sensor which can be implanted in proximity with an artery. The expected benefits for this type of sensor are mainly to reduce the problems associated with the use of bulk devices through the day and during several days. Such a sensor could give precise blood pressure readings in a continuous or periodic form, i.e. information that is especially important for some critical cases of hypertension patients.

Spatially digitized tactile pressure sensors with tunable sensitivity and sensing range.

PubMed

Choi, Eunsuk; Sul, Onejae; Hwang, Soonhyung; Cho, Joonhyung; Chun, Hyunsuk; Kim, Hongjun; Lee, Seung-Beck

2014-10-24

When developing an electronic skin with touch sensation, an array of tactile pressure sensors with various ranges of pressure detection need to be integrated. This requires low noise, highly reliable sensors with tunable sensing characteristics. We demonstrate the operation of tactile pressure sensors that utilize the spatial distribution of contact electrodes to detect various ranges of tactile pressures. The device consists of a suspended elastomer diaphragm, with a carbon nanotube thin-film on the bottom, which makes contact with the electrodes on the substrate with applied pressure. The electrodes separated by set distances become connected in sequence with tactile pressure, enabling consecutive electrodes to produce a signal. Thus, the pressure is detected not by how much of a signal is produced but by which of the electrodes is registering an output. By modulating the diaphragm diameter, and suspension height, it was possible to tune the pressure sensitivity and sensing range. Also, adding a fingerprint ridge structure enabled the sensor to detect the periodicity of sub-millimeter grating patterns on a silicon wafer.

Piezoresistive silicon pressure sensors in cryogenic environment

NASA Technical Reports Server (NTRS)

Kahng, Seun K.; Chapman, John J.

1989-01-01

This paper presents data on low-temperature measurements of silicon pressure sensors. It was found that both the piezoresistance coefficients and the charge-carrier mobility increase with decreasing temperature. For lightly doped semiconductor materials, the density of free charge carriers decreases with temperature and can freeze out eventually. However, the effect of carrier freeze-out can be minimized by increasing the impurity content to higher levels, at which the temperature dependency of piezoresistance coefficients is reduced. An impurity density of 1 x 10 to the 19th/cu cm was found to be optimal for cryogenic applications of pressure sensor dies.

Non-destructive residual pressure self-measurement method for the sensing chip of optical Fabry-Perot pressure sensor.

PubMed

Wang, Xue; Wang, Shuang; Jiang, Junfeng; Liu, Kun; Zhang, Xuezhi; Xiao, Mengnan; Xiao, Hai; Liu, Tiegen

2017-12-11

We introduce a simple residual pressure self-measurement method for the Fabry-Perot (F-P) cavity of optical MEMS pressure sensor. No extra installation is required and the structure of the sensor is unchanged. In the method, the relationship between residual pressure and external pressure under the same diaphragm deflection condition at different temperatures is analyzed by using the deflection formula of the circular plate with clamped edges and the ideal gas law. Based on this, the residual pressure under the flat condition can be obtained by pressure scanning process and calculation process. We carried out the experiment to compare the residual pressures of two batches MEMS sensors fabricated by two kinds of bonding process. The measurement result indicates that our approach is reliable enough for the measurement.

Advanced Packaging Technology Used in Fabricating a High-Temperature Silicon Carbide Pressure Sensor

NASA Technical Reports Server (NTRS)

Beheim, Glenn M.

2003-01-01

The development of new aircraft engines requires the measurement of pressures in hot areas such as the combustor and the final stages of the compressor. The needs of the aircraft engine industry are not fully met by commercially available high-temperature pressure sensors, which are fabricated using silicon. Kulite Semiconductor Products and the NASA Glenn Research Center have been working together to develop silicon carbide (SiC) pressure sensors for use at high temperatures. At temperatures above 850 F, silicon begins to lose its nearly ideal elastic properties, so the output of a silicon pressure sensor will drift. SiC, however, maintains its nearly ideal mechanical properties to extremely high temperatures. Given a suitable sensor material, a key to the development of a practical high-temperature pressure sensor is the package. A SiC pressure sensor capable of operating at 930 F was fabricated using a newly developed package. The durability of this sensor was demonstrated in an on-engine test. The SiC pressure sensor uses a SiC diaphragm, which is fabricated using deep reactive ion etching. SiC strain gauges on the surface of the diaphragm sense the pressure difference across the diaphragm. Conventionally, the SiC chip is mounted to the package with the strain gauges outward, which exposes the sensitive metal contacts on the chip to the hostile measurement environment. In the new Kulite leadless package, the SiC chip is flipped over so that the metal contacts are protected from oxidation by a hermetic seal around the perimeter of the chip. In the leadless package, a conductive glass provides the electrical connection between the pins of the package and the chip, which eliminates the fragile gold wires used previously. The durability of the leadless SiC pressure sensor was demonstrated when two 930 F sensors were tested in the combustor of a Pratt & Whitney PW4000 series engine. Since the gas temperatures in these locations reach 1200 to 1300 F, the sensors were

Touch-mode capacitive pressure sensor with graphene-polymer heterostructure membrane

NASA Astrophysics Data System (ADS)

Berger, Christian; Phillips, Rory; Pasternak, Iwona; Sobieski, Jan; Strupinski, Wlodek; Vijayaraghavan, Aravind

2018-01-01

We describe the fabrication and characterisation of a touch-mode capacitive pressure sensor (TMCPS) with a robust design that comprises a graphene-polymer heterostructure film, laminated onto the silicon dioxide surface of a silicon wafer, incorporating a SU-8 spacer grid structure. The spacer grid structure allows the flexible graphene-polymer film to be partially suspended above the substrate, such that a pressure on the membrane results in a reproducible deflection, even after exposing the membrane to pressures over 10 times the operating range. Sensors show reproducible pressure transduction in water submersion at varying depths under static and dynamic loading. The measured capacitance change in response to pressure is in good agreement with an analytical model of clamped plates in touch mode. The device shows a pressure sensitivity of 27.1 +/- 0.5 fF Pa-1 over a pressure range of 0.5 kPa-8.5 kPa. In addition, we demonstrate the operation of this device as a force-touch sensor in air.

Pressure sensor based on the fiber-optic extrinsic Fabry-Perot interferometer

NASA Astrophysics Data System (ADS)

Yu, Qingxu; Zhou, Xinlei

2011-03-01

Pressure sensors based on fiber-optic extrinsic Fabry-Perot interferometer (EFPI) have been extensively applied in various industrial and biomedical fields. In this paper, some key improvements of EFPI-based pressure sensors such as the controlled thermal bonding technique, diaphragm-based EFPI sensors, and white light interference technology have been reviewed. Recent progress on signal demodulation method and applications of EFPI-based pressure sensors has been introduced. Signal demodulation algorithms based on the cross correlation and mean square error (MSE) estimation have been proposed for retrieving the cavity length of EFPI. Absolute measurement with a resolution of 0.08 nm over large dynamic range has been carried out. For downhole monitoring, an EFPI and a fiber Bragg grating (FBG) cascade multiplexing fiber-optic sensor system has been developed, which can operate in temperature 300 °C with a good long-term stability and extremely low temperature cross-sensitivity. Diaphragm-based EFPI pressure sensors have been successfully used for low pressure and acoustic wave detection. Experimental results show that a sensitivity of 31 mV/Pa in the frequency range of 100 Hz to 12.7 kHz for aeroacoustic wave detection has been obtained.

Flexible Piezoelectric-Induced Pressure Sensors for Static Measurements Based on Nanowires/Graphene Heterostructures.

PubMed

Chen, Zefeng; Wang, Zhao; Li, Xinming; Lin, Yuxuan; Luo, Ningqi; Long, Mingzhu; Zhao, Ni; Xu, Jian-Bin

2017-05-23

The piezoelectric effect is widely applied in pressure sensors for the detection of dynamic signals. However, these piezoelectric-induced pressure sensors have challenges in measuring static signals that are based on the transient flow of electrons in an external load as driven by the piezopotential arisen from dynamic stress. Here, we present a pressure sensor with nanowires/graphene heterostructures for static measurements based on the synergistic mechanisms between strain-induced polarization charges in piezoelectric nanowires and the caused change of carrier scattering in graphene. Compared to the conventional piezoelectric nanowire or graphene pressure sensors, this sensor is capable of measuring static pressures with a sensitivity of up to 9.4 × 10 -3 kPa -1 and a fast response time down to 5-7 ms. This demonstration of pressure sensors shows great potential in the applications of electronic skin and wearable devices.

Micro-Pressure Sensors for Future Mars Missions

NASA Technical Reports Server (NTRS)

Catling, David C.

1996-01-01

The joint research interchange effort was directed at the following principal areas: u further development of NASA-Ames' Mars Micro-meteorology mission concept as a viable NASA space mission especially with regard to the science and instrument specifications u interaction with the flight team from NASA's New Millennium 'Deep-Space 2' (DS-2) mission with regard to selection and design of micro-pressure sensors for Mars u further development of micro-pressure sensors suitable for Mars The research work undertaken in the course of the Joint Research Interchange should be placed in the context of an ongoing planetary exploration objective to characterize the climate system on Mars. In particular, a network of small probes globally-distributed on the surface of the planet has often been cited as the only way to address this particular science goal. A team from NASA Ames has proposed such a mission called the Micrometeorology mission, or 'Micro-met' for short. Surface pressure data are all that are required, in principle, to calculate the Martian atmospheric circulation, provided that simultaneous orbital measurements of the atmosphere are also obtained. Consequently, in the proposed Micro-met mission a large number of landers would measure barometric pressure at various locations around Mars, each equipped with a micro-pressure sensor. Much of the time on the JRI was therefore spent working with the engineers and scientists concerned with Micro-met to develop this particular mission concept into a more realistic proposition.

A High-Temperature Piezoresistive Pressure Sensor with an Integrated Signal-Conditioning Circuit.

PubMed

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Xiong, Jijun

2016-06-18

This paper focuses on the design and fabrication of a high-temperature piezoresistive pressure sensor with an integrated signal-conditioning circuit, which consists of an encapsulated pressure-sensitive chip, a temperature compensation circuit and a signal-conditioning circuit. A silicon on insulation (SOI) material and a standard MEMS process are used in the pressure-sensitive chip fabrication, and high-temperature electronic components are adopted in the temperature-compensation and signal-conditioning circuits. The entire pressure sensor achieves a hermetic seal and can be operated long-term in the range of -50 °C to 220 °C. Unlike traditional pressure sensor output voltage ranges (in the dozens to hundreds of millivolts), the output voltage of this sensor is from 0 V to 5 V, which can significantly improve the signal-to-noise ratio and measurement accuracy in practical applications of long-term transmission based on experimental verification. Furthermore, because this flexible sensor's output voltage is adjustable, general follow-up pressure transmitter devices for voltage converters need not be used, which greatly reduces the cost of the test system. Thus, the proposed high-temperature piezoresistive pressure sensor with an integrated signal-conditioning circuit is expected to be highly applicable to pressure measurements in harsh environments.

Validation of a new micro-manometer pressure sensor for cardiovascular measurements in mice.

PubMed

Trevino, Rodolfo J; Jones, Douglas L; Escobedo, Daniel; Porterfield, John; Larson, Erik; Chisholm, Gary B; Barton, Amanda; Feldman, Marc D

2010-01-01

Abstract The Scisense (London, ON, Canada) micro-manometer pressure sensor is currently being used by investigators to evaluate cardiovascular physiology in mice, but has not been validated to date. The purpose of the current study is to compare the 1.2 F Scisense pressure sensor to the current gold standard produced by Millar Instruments (Houston, TX) (1.4 F). In vitro comparisons were preformed including temperature drift, frequency response analysis up to 250 Hz, and damping coefficient and natural frequency determined via a pop test. The authors also performed in vivo comparisons including pressure drift, dose-response studies to IV isoproterenol, maximum adrenergic stimulation with IV dobutamine, and simultaneous placement of both micro-manometer pressure sensors in the same intact murine hearts. The authors conclude that both sensors are equivalent, and that the Scisense pressure sensor represents an alternative to the current gold standard, the Millar micro-manometer pressure sensor for in vivo pressure measurements in the mouse.

Piezoresistive pressure sensor with high sensitivity for medical application using peninsula-island structure

NASA Astrophysics Data System (ADS)

Xu, Tingzhong; Wang, Hongyan; Xia, Yong; Zhao, Zhiming; Huang, Mimi; Wang, Jiuhong; Zhao, Libo; Zhao, Yulong; Jiang, Zhuangde

2017-12-01

A novel micro-electromechanical systems piezoresistive pressure sensor with a diagonally positioned peninsula-island structure has high sensitivity for ultralow- pressure measurement. The pressure sensor was designed with a working range of 0-500 Pa and had a high sensitivity of 0.06 mV·V-1·Pa-1. The trade-off between high sensitivity and linearity was alleviated. Moreover, the influence of the installation angle on the sensing chip output was analyzed, and an application experiment of the sensor was conducted using the built pipettor test platform. Findings indicated that the proposed pressure sensor had sufficient resolution ability and accuracy to detect the pressure variation in the pipettor chamber. Therefore, the proposed pressure sensor has strong potential for medical equipment application.

Methods and Systems for Configuring Sensor Acquisition Based on Pressure Steps

NASA Technical Reports Server (NTRS)

DeDonato, Mathew (Inventor)

2015-01-01

Technologies are provided for underwater measurements. A system includes an underwater vessels including: a plurality of sensors disposed thereon for measuring underwater properties; and a programmable controller configured to selectively activate the plurality of sensors based at least in part on underwater pressure. A user may program at what pressure ranges certain sensors are activated to measure selected properties, and may also program the ascent/descent rate of the underwater vessel, which is correlated with the underwater pressure.

Effects of ambient temperature and water vapor on chamber pressure and oxygen level during low atmospheric pressure stunning of poultry.

PubMed

Holloway, Paul H; Pritchard, David G

2017-08-01

The characteristics of the vacuum used in a low atmospheric pressure stunning system to stun (render unconscious) poultry prior to slaughter are described. A vacuum chamber is pumped by a wet screw compressor. The vacuum pressure is reduced from ambient atmospheric pressure to an absolute vacuum pressure of ∼250 Torr (∼33 kPa) in ∼67 sec with the vacuum gate valve fully open. At ∼250 Torr, the sliding gate valve is partially closed to reduce effective pumping speed, resulting in a slower rate of decreasing pressure. Ambient temperature affects air density and water vapor pressure and thereby oxygen levels and the time at the minimum total pressure of ∼160 Torr (∼21 kPa) is varied from ∼120 to ∼220 sec to ensure an effective stun within the 280 seconds of each cycle. The reduction in total pressure results in a gradual reduction of oxygen partial pressure that was measured by a solid-state electrochemical oxygen sensor. The reduced oxygen pressure leads to hypoxia, which is recognized as a humane method of stunning poultry. The system maintains an oxygen concentration of <5% for at least 2 minutes, which ensures that birds are irreversibly stunned. Calculated pump down (pressure versus time) data match experimental data very closely because the programmable logic controller and the human machine interface enable precise and accurate control. The vacuum system operates in the turbulent viscous flow regime, and is best characterized by absolute vacuum pressure rather than gauge pressure. Neither the presence of broiler chickens nor different fore-line pipe designs of four parallel commercial systems affected the pressure-time data. Water in wet air always reduces the oxygen concentrations to a value lower than in dry air. The partial pressure of water and oxygen were found to depend on the pump down parameters due to the formation of fog in the chamber and desorption of water from the birds and the walls of the vacuum chamber. © The Author 2017

Ultrahigh vacuum/high pressure chamber for surface x-ray diffraction experiments

NASA Astrophysics Data System (ADS)

Bernard, P.; Peters, K.; Alvarez, J.; Ferrer, S.

1999-02-01

We describe an ultrahigh vacuum chamber that can be internally pressurized to several bars and that is designed to perform surface x-ray diffraction experiments on solid-gas interfaces. The chamber has a cylindrical beryllium window that serves as the entrance and exit for the x rays. The sample surface can be ion bombarded with an ancillary ion gun and annealed to 1200 K.

Novel High Temperature Capacitive Pressure Sensor Utilizing SiC Integrated Circuit Twin Ring Oscillators

NASA Technical Reports Server (NTRS)

Scardelletti, M.; Neudeck, P.; Spry, D.; Meredith, R.; Jordan, J.; Prokop, N.; Krasowski, M.; Beheim, G.; Hunter, G.

2017-01-01

This paper describes initial development and testing of a novel high temperature capacitive pressure sensor system. The pressure sensor system consists of two 4H-SiC 11-stage ring oscillators and a SiCN capacitive pressure sensor. One oscillator has the capacitive pressure sensor fixed at one node in its feedback loop and varies as a function of pressure and temperature while the other provides a pressure-independent reference frequency which can be used to temperature compensate the output of the first oscillator. A two-day repeatability test was performed up to 500C on the oscillators and the oscillator fundamental frequency changed by only 1. The SiCN capacitive pressure sensor was characterized at room temperature from 0 to 300 psi. The sensor had an initial capacitance of 3.76 pF at 0 psi and 1.75 pF at 300 psi corresponding to a 54 change in capacitance. The integrated pressure sensor system was characterized from 0 to 300 psi in steps of 50 psi over a temperature range of 25 to 500C. The pressure sensor system sensitivity was 0.113 kHzpsi at 25C and 0.026 kHzpsi at 500C.

A Quad-Cantilevered Plate micro-sensor for intracranial pressure measurement.

PubMed

Lalkov, Vasko; Qasaimeh, Mohammad A

2017-07-01

This paper proposes a new design for pressure-sensing micro-plate platform to bring higher sensitivity to a pressure sensor based on piezoresistive MEMS sensing mechanism. The proposed design is composed of a suspended plate having four stepped cantilever beams connected to its corners, and thus defined as Quad-Cantilevered Plate (QCP). Finite element analysis was performed to determine the optimal design for sensitivity and structural stability under a range of applied forces. Furthermore, a piezoresistive analysis was performed to calculate sensor sensitivity. Both the maximum stress and the change in resistance of the piezoresistor associated with the QCP were found to be higher compared to previously published designs, and linearly related to the applied pressure as desired. Therefore, the QCP demonstrates greater sensitivity, and could be potentially used as an efficient pressure sensor for intracranial pressure measurement.

Graphene-based inline pressure sensor integrated with microfluidic elastic tube

NASA Astrophysics Data System (ADS)

Inoue, Nagisa; Onoe, Hiroaki

2018-01-01

We propose an inline pressure sensor composed of a polydimethylsiloxane (PDMS) microfluidic tube integrated with graphene sheets. The PDMS tube was fabricated through molding, and a multilayered graphene sheet was transferred on the surface of the PDMS tube. The pressure inside the tube was monitored using the changes in the electrical resistance of the transferred graphene. The proposed pressure sensor could be suitable for precise pressure measurement for a small amount of fluid in microfluidic systems including organ-on-a-chip devices.

Vacuum and low oxygen pressure influence on BaFe12O19 film deposited by pulse laser deposition

NASA Astrophysics Data System (ADS)

Kumar, Pawan; Gaur, Anurag; Choudhary, R. J.

2018-05-01

BaFe12O19 hexaferrite thin films are deposited on Si (111) substrate by the pulse laser deposition (PLD) technique in high vacuum 10-6 Torr and low oxygen pressure (10 mTorr) at 650°C substrate temperature. The effects of high vacuum and low pressure on magnetic and optical properties are studied. These films are characterized by the x-ray diffractometer (XRD), SQUID-VSM magnetometer, and Photo-luminescence spectroscopy. XRD pattern reveals that the BaFe12O19 film well formed in both environments without any impurity pick. High magnetic saturazation 317 emu/cm3 and coercivity 130 Oe are observed for the film deposited in vacuum. Photoluminescence emission spectrum of BaFe12O19 film reveals that the higher intensity emission peak at ˜372 nm under the excitation wavelength of 270 nm is observed for the film grown in vacuum.

A Comparative Study of Sound Speed in Air at Room Temperature between a Pressure Sensor and a Sound Sensor

ERIC Educational Resources Information Center

Amrani, D.

2013-01-01

This paper deals with the comparison of sound speed measurements in air using two types of sensor that are widely employed in physics and engineering education, namely a pressure sensor and a sound sensor. A computer-based laboratory with pressure and sound sensors was used to carry out measurements of air through a 60 ml syringe. The fast Fourier…

Parylene-on-oil packaging for long-term implantable pressure sensors.

PubMed

Shapero, Aubrey M; Liu, Yang; Tai, Yu-Chong

2016-08-01

This paper reports and analyzes the feasibility study of a parylene-on-oil encapsulation packaging method of pressure sensors targeted for long-term implantation. Commercial barometric digital-output pressure sensors are enclosed in silicone oil and then encapsulated in situ with parylene-C or -D (PA-C, PA-D) chemical vapor deposition. Experimentally, sensors encapsulated with 30,000 cSt silicone oil and 27 μm PA-D show good performance for 6 weeks in 77 °C saline with >99 % of original sensitivity, corresponding to an extrapolated lifetime of around 21 months in 37 °C saline. This work shows that, with proper designs, such a packaging method can preserve the original pressure sensor sensitivity without offset, validated throughout accelerated lifetime tests. In experiments, wires on the prototypes are used for external electronics but it is found that they contributed to early failures, which would be absent in real wireless versions, indicating a potential for even longer lifetimes. Finally, a verified model is presented to predict the pressure sensor sensitivity of parylene-on-oil packaging with and without the presence of a bubble in the oil.

Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes.

PubMed

Pishvar, Maya; Amirkhosravi, Mehrad; Altan, M Cengiz

2018-05-17

This work demonstrates a protocol to improve the quality of composite laminates fabricated by wet lay-up vacuum bag processes using the recently developed magnet assisted composite manufacturing (MACM) technique. In this technique, permanent magnets are utilized to apply a sufficiently high consolidation pressure during the curing stage. To enhance the intensity of the magnetic field, and thus, to increase the magnetic compaction pressure, the magnets are placed on a magnetic top plate. First, the entire procedure of preparing the composite lay-up on a magnetic bottom steel plate using the conventional wet lay-up vacuum bag process is described. Second, placement of a set of Neodymium-Iron-Boron permanent magnets, arranged in alternating polarity, on the vacuum bag is illustrated. Next, the experimental procedures to measure the magnetic compaction pressure and volume fractions of the composite constituents are presented. Finally, methods used to characterize microstructure and mechanical properties of composite laminates are discussed in detail. The results prove the effectiveness of the MACM method in improving the quality of wet lay-up vacuum bag laminates. This method does not require large capital investment for tooling or equipment and can also be used to consolidate geometrically complex composite parts by placing the magnets on a matching top mold positioned on the vacuum bag.

Passive tire pressure sensor and method

DOEpatents

Pfeifer, Kent Bryant; Williams, Robert Leslie; Waldschmidt, Robert Lee; Morgan, Catherine Hook

2006-08-29

A surface acoustic wave device includes a micro-machined pressure transducer for monitoring tire pressure. The device is configured having a micro-machined cavity that is sealed with a flexible conductive membrane. When an external tire pressure equivalent to the cavity pressure is detected, the membrane makes contact with ridges on the backside of the surface acoustic wave device. The ridges are electrically connected to conductive fingers of the device. When the detected pressure is correct, selected fingers on the device will be grounded producing patterned acoustic reflections to an impulse RF signal. When the external tire pressure is less than the cavity reference pressure, a reduced reflected signal to the receiver results. The sensor may further be constructed so as to identify itself by a unique reflected identification pulse series.

Passive tire pressure sensor and method

DOEpatents

Pfeifer, Kent Bryant; Williams, Robert Leslie; Waldschmidt, Robert Lee; Morgan, Catherine Hook

2007-09-04

A surface acoustic wave device includes a micro-machined pressure transducer for monitoring tire pressure. The device is configured having a micro-machined cavity that is sealed with a flexible conductive membrane. When an external tire pressure equivalent to the cavity pressure is detected, the membrane makes contact with ridges on the backside of the surface acoustic wave device. The ridges are electrically connected to conductive fingers of the device. When the detected pressure is correct, selected fingers on the device will be grounded producing patterned acoustic reflections to an impulse RF signal. When the external tire pressure is less than the cavity reference pressure, a reduced reflected signal to the receiver results. The sensor may further be constructed so as to identify itself by a unique reflected identification pulse series.

A Micromachined Piezoresistive Pressure Sensor with a Shield Layer

PubMed Central

Cao, Gang; Wang, Xiaoping; Xu, Yong; Liu, Sheng

2016-01-01

This paper presents a piezoresistive pressure sensor with a shield layer for improved stability. Compared with the conventional piezoresistive pressure sensors, the new one reported in this paper has an n-type shield layer that covers p-type piezoresistors. This shield layer aims to minimize the impact of electrical field and reduce the temperature sensitivity of piezoresistors. The proposed sensors have been successfully fabricated by bulk-micromachining techniques. A sensitivity of 0.022 mV/V/kPa and a maximum non-linearity of 0.085% FS are obtained in a pressure range of 1 MPa. After numerical simulation, the role of the shield layer has been experimentally investigated. It is demonstrated that the shield layer is able to reduce the drift caused by electrical field and ambient temperature variation. PMID:27529254

The use of combined thermal/pressure polyvinylidene fluoride film airflow sensor in polysomnography.

PubMed

Kryger, Meir; Eiken, Todd; Qin, Li

2013-12-01

The technologies recommended by the American Academy of Sleep Medicine (AASM) to monitor airflow in polysomnography (PSG) include the simultaneous monitoring of two physical variables: air temperature (for thermal airflow) and air pressure (for nasal pressure). To comply with airflow monitoring standards in the sleep lab setting thus often requires the patient to wear two sensors under the nose during testing. We hypothesized that a single combined thermal/pressure sensor using polyvinylidene fluoride (PVDF) film responsive to both airflow temperature and pressure would be effective in documenting abnormal breathing events during sleep. Sixty patients undergoing routine PSG testing to rule out obstructive sleep apnea at two different sleep laboratories were asked to wear a third PVDF airflow sensor in addition to the traditional thermal sensor and pressure sensor. Apnea and hypopnea events were scored by the sleep lab technologists using the AASM guidelines (CMS option) using the thermal sensor for apnea and the pressure sensor for hypopnea (scorer 1). The digital PSG data were also forwarded to an outside registered polysomnographic technologist for scoring of respiratory events detected in the PVDF airflow channels (scorer 2). The Pearson correlation coefficient, r, between apnea and hypopnea indices obtained using the AASM sensors and the combined PVDF sensor was almost unity for the four calculated indices: apnea-hypopnea index (0.990), obstructive apnea index (0.992), hypopnea index (0.958), and central apnea index (1.0). The slope of the four relationships was virtually unity and the coefficient of determination (r (2)) was also close to 1. The results of intraclass correlation coefficients (>0.95) and Bland-Altman plots also provide excellent agreement between the combined PVDF sensor and the AASM sensors. The indices used to calculate apnea severity obtained with the combined PVDF thermal and pressure sensor were equivalent to those obtained using AASM

Generation of a medium vacuum pressure by using two different pumping methods in the KRISS dynamic flow-control system

NASA Astrophysics Data System (ADS)

Hong, S. S.; Lim, J. Y.; Khan, W.

2014-02-01

Pumping systems with large vacuum chambers have numerous applications in the process industry: for example, mixing of various types of gases as in the semiconductor industry, the calibration of vacuum gauges, the measurement of outgassing rates of various materials in the field of space technology, etc. Most often, these systems are used in the medium vacuum range (10-1 Pa-102 Pa) and in the dynamically-generated pressure mode. We have designed and developed a new dynamic flow system at the KRISS (Korea Research Institute of Standards and Science) that can be used for such applications with reliability in the range from 0.1 Pa - 133 Pa. In this report, the design philosophy, operational procedure and experimental data for the generated stable pressure points in the chamber of the system are discussed. The data consist the pressure points generated in the medium vacuum range while pumping the chamber of the system by using two different methods: first by using a dry scroll pump and then by using a combination of a turbomolecular pump backed by the same scroll pump. The relative standard deviations in the pressure points were calculated and were found to be greater than 1.5% for the scroll pump and less than 0.5% for the turbomolecular pump.

An Optical Fibre Depth (Pressure) Sensor for Remote Operated Vehicles in Underwater Applications

PubMed Central

Duraibabu, Dinesh Babu; Poeggel, Sven; Omerdic, Edin; Capocci, Romano; Lewis, Elfed; Newe, Thomas; Leen, Gabriel; Toal, Daniel; Dooly, Gerard

2017-01-01

A miniature sensor for accurate measurement of pressure (depth) with temperature compensation in the ocean environment is described. The sensor is based on an optical fibre Extrinsic Fabry-Perot interferometer (EFPI) combined with a Fibre Bragg Grating (FBG). The EFPI provides pressure measurements while the Fibre Bragg Grating (FBG) provides temperature measurements. The sensor is mechanically robust, corrosion-resistant and suitable for use in underwater applications. The combined pressure and temperature sensor system was mounted on-board a mini remotely operated underwater vehicle (ROV) in order to monitor the pressure changes at various depths. The reflected optical spectrum from the sensor was monitored online and a pressure or temperature change caused a corresponding observable shift in the received optical spectrum. The sensor exhibited excellent stability when measured over a 2 h period underwater and its performance is compared with a commercially available reference sensor also mounted on the ROV. The measurements illustrates that the EFPI/FBG sensor is more accurate for depth measurements (depth of ~0.020 m). PMID:28218727

Review on pressure sensors for structural health monitoring

NASA Astrophysics Data System (ADS)

Sikarwar, Samiksha; Satyendra; Singh, Shakti; Yadav, Bal Chandra

2017-12-01

This paper reports the state of art in a variety of pressure and the detailed study of various matrix based pressure sensors. The performances of the bridges, buildings, etc. are threatened by earthquakes, material degradations, and other environmental effects. Structural health monitoring (SHM) is crucial to protect the people and also for assets planning. This study is a contribution in developing the knowledge about self-sensing smart materials and structures for the construction industry. It deals with the study of self-sensing as well as mechanical and electrical properties of different matrices based on pressure sensors. The relationships among the compression, tensile strain, and crack length with electrical resistance change are also reviewed.

Integrated Cryogenic Propulsion Test Article Thermal Vacuum Hotfire Testing

NASA Technical Reports Server (NTRS)

Morehead, Robert L.; Melcher, J. C.; Atwell, Matthew J.; Hurlbert, Eric A.

2017-01-01

In support of a facility characterization test, the Integrated Cryogenic Propulsion Test Article (ICPTA) was hotfire tested at a variety of simulated altitude and thermal conditions in the NASA Glenn Research Center Plum Brook Station In-Space Propulsion Thermal Vacuum Chamber (formerly B2). The ICPTA utilizes liquid oxygen and liquid methane propellants for its main engine and four reaction control engines, and uses a cold helium system for tank pressurization. The hotfire test series included high altitude, high vacuum, ambient temperature, and deep cryogenic environments, and several hundred sensors on the vehicle collected a range of system level data useful to characterize the operation of an integrated LOX/Methane spacecraft in the space environment - a unique data set for this propellant combination.

Experimental Verification of Steel Pipe Collapse under Vacuum Pressure Conditions

NASA Astrophysics Data System (ADS)

Autrique, R.; Rodal, E.

2016-11-01

Steel pipes are used widely in hydroelectric systems and in pumping systems. Both systems are subject to hydraulic transient effects caused by changes in boundary conditions, such as sudden valve closures, pump failures, or accidents. Water column separation, and its associated vaporization pressure inside the pipe, can cause the collapse of thin walled steel pipes subject to atmospheric pressure, as happened during the well known Oigawa Power Plant accident in Japan, in 1950. The conditions under which thin walled pipes subject to external pressure can collapse have been studied mathematically since the second half of the XIX century, with classical authors Southwell and Von Mises obtaining definitive equations for long and short pipes in the second decade of the XX century, in which the fundamental variables are the diameter to thickness ratio D/t and the length to diameter ratio L/D. In this paper, the predicted critical D/t ratio for steel pipe collapse is verified experimentally, in a physical model able to reproduce hydraulic transients, generating vacuum pressures through rapid upstream valve closures.

Calibration Of Partial-Pressure-Of-Oxygen Sensors

NASA Technical Reports Server (NTRS)

Yount, David W.; Heronimus, Kevin

1995-01-01

Report and analysis of, and discussion of improvements in, procedure for calibrating partial-pressure-of-oxygen sensors to satisfy Spacelab calibration requirements released. Sensors exhibit fast drift, which results in short calibration period not suitable for Spacelab. By assessing complete process of determining total drift range available, calibration procedure modified to eliminate errors and still satisfy requirements without compromising integrity of system.

High-sensitivity pressure sensor based on fiber Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Wu, Yue; Xu, Yao; Yang, Yuguang; Jin, Wenxing; Jiang, Youchao; Shen, Ya; Jian, Shuisheng

2017-10-01

In this paper we propose and experimentally demonstrate an optical fiber structure sensor based on a Mach-Zehnder interferometer for pressure measurement. The fiber sensor is composed of a single-mode-no-core-single-mode structure, a section of capillary pure silica tube and refractive index matching fluid (RIMF). As the pressure decreases, the sealed air in the tube expands and the liquid level of the RIMF increases, which causes a wavelength shift of the interferometer. The measurement of the pressure variation can thus be achieved by monitoring the wavelength shift. The experimental results agree well with the numerical simulation, and a maximum pressure sensitivity of 266.6 nm Mpa-1 is achieved experimentally. Furthermore, the proposed fiber sensor has the potential to obtain higher sensitivity by enlarging the length of the air cavity.

Development of Clinically Relevant Implantable Pressure Sensors: Perspectives and Challenges

PubMed Central

Clausen, Ingelin; Glott, Thomas

2014-01-01

This review describes different aspects to consider when developing implantable pressure sensor systems. Measurement of pressure is in general highly important in clinical practice and medical research. Due to the small size, light weight and low energy consumption Micro Electro Mechanical Systems (MEMS) technology represents new possibilities for monitoring of physiological parameters inside the human body. Development of clinical relevant sensors requires close collaboration between technological experts and medical clinicians. Site of operation, size restrictions, patient safety, and required measurement range and resolution, are only some conditions that must be taken into account. An implantable device has to operate under very hostile conditions. Long-term in vivo pressure measurements are particularly demanding because the pressure sensitive part of the sensor must be in direct or indirect physical contact with the medium for which we want to detect the pressure. New sensor packaging concepts are demanded and must be developed through combined effort between scientists in MEMS technology, material science, and biology. Before launching a new medical device on the market, clinical studies must be performed. Regulatory documents and international standards set the premises for how such studies shall be conducted and reported. PMID:25248071

Development of clinically relevant implantable pressure sensors: perspectives and challenges.

PubMed

Clausen, Ingelin; Glott, Thomas

2014-09-22

This review describes different aspects to consider when developing implantable pressure sensor systems. Measurement of pressure is in general highly important in clinical practice and medical research. Due to the small size, light weight and low energy consumption Micro Electro Mechanical Systems (MEMS) technology represents new possibilities for monitoring of physiological parameters inside the human body. Development of clinical relevant sensors requires close collaboration between technological experts and medical clinicians.  Site of operation, size restrictions, patient safety, and required measurement range and resolution, are only some conditions that must be taken into account. An implantable device has to operate under very hostile conditions. Long-term in vivo pressure measurements are particularly demanding because the pressure sensitive part of the sensor must be in direct or indirect physical contact with the medium for which we want to detect the pressure. New sensor packaging concepts are demanded and must be developed through combined effort between scientists in MEMS technology, material science, and biology. Before launching a new medical device on the market, clinical studies must be performed. Regulatory documents and international standards set the premises for how such studies shall be conducted and reported.

Particle-based optical pressure sensors for 3D pressure mapping.

PubMed

Banerjee, Niladri; Xie, Yan; Chalaseni, Sandeep; Mastrangelo, Carlos H

2015-10-01

This paper presents particle-based optical pressure sensors for in-flow pressure sensing, especially for microfluidic environments. Three generations of pressure sensitive particles have been developed- flat planar particles, particles with integrated retroreflectors and spherical microballoon particles. The first two versions suffer from pressure measurement dependence on particles orientation in 3D space and angle of interrogation. The third generation of microspherical particles with spherical symmetry solves these problems making particle-based manometry in microfluidic environment a viable and efficient methodology. Static and dynamic pressure measurements have been performed in liquid medium for long periods of time in a pressure range of atmospheric to 40 psi. Spherical particles with radius of 12 μm and balloon-wall thickness of 0.5 μm are effective for more than 5 h in this pressure range with an error of less than 5%.

Characteristics research of pressure sensor based on nanopolysilicon thin films resistors

NASA Astrophysics Data System (ADS)

Zhao, Xiaofeng; Li, Dandan; Wen, Dianzhong

2017-10-01

To further improve the sensitivity temperature characteristics of pressure sensor, a kind of pressure sensor taking nanopolysilicon thin films as piezoresistors is proposed in this paper. On the basis of the microstructure analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) tests, the preparing process of nanopolysilicon thin films is optimized. The effects of film thickness and annealing temperature on the micro-structure of nanopolysilicon thin films were studied, respectively. In order to realize the measurement of external pressure, four nanopolysilicon thin films resistors were arranged at the edges of square silicon diaphragm connected to a Wheatstone bridge, and the chip of the sensor was designed and fabricated on a 〈100〉 orientation silicon wafer by microelectromechanical system (MEMS) technology. Experimental result shows that when I = 6.80 mA, the sensitivity of the sensor PS-1 is 0.308 mV/kPa, and the temperature coefficient of sensitivity (TCS) is about -1742 ppm/∘C in the range of -40-140∘C. It is possible to obviously improve the sensitivity temperature characteristics of pressure sensor by the proposed sensors.

A High-Temperature Piezoresistive Pressure Sensor with an Integrated Signal-Conditioning Circuit

PubMed Central

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Xiong, Jijun

2016-01-01

This paper focuses on the design and fabrication of a high-temperature piezoresistive pressure sensor with an integrated signal-conditioning circuit, which consists of an encapsulated pressure-sensitive chip, a temperature compensation circuit and a signal-conditioning circuit. A silicon on insulation (SOI) material and a standard MEMS process are used in the pressure-sensitive chip fabrication, and high-temperature electronic components are adopted in the temperature-compensation and signal-conditioning circuits. The entire pressure sensor achieves a hermetic seal and can be operated long-term in the range of −50 °C to 220 °C. Unlike traditional pressure sensor output voltage ranges (in the dozens to hundreds of millivolts), the output voltage of this sensor is from 0 V to 5 V, which can significantly improve the signal-to-noise ratio and measurement accuracy in practical applications of long-term transmission based on experimental verification. Furthermore, because this flexible sensor’s output voltage is adjustable, general follow-up pressure transmitter devices for voltage converters need not be used, which greatly reduces the cost of the test system. Thus, the proposed high-temperature piezoresistive pressure sensor with an integrated signal-conditioning circuit is expected to be highly applicable to pressure measurements in harsh environments. PMID:27322288

Highly Sensitive and Patchable Pressure Sensors Mimicking Ion-Channel-Engaged Sensory Organs.

PubMed

Chun, Kyoung-Yong; Son, Young Jun; Han, Chang-Soo

2016-04-26

Biological ion channels have led to much inspiration because of their unique and exquisite operational functions in living cells. Specifically, their extreme and dynamic sensing abilities can be realized by the combination of receptors and nanopores coupled together to construct an ion channel system. In the current study, we demonstrated that artificial ion channel pressure sensors inspired by nature for detecting pressure are highly sensitive and patchable. Our ion channel pressure sensors basically consisted of receptors and nanopore membranes, enabling dynamic current responses to external forces for multiple applications. The ion channel pressure sensors had a sensitivity of ∼5.6 kPa(-1) and a response time of ∼12 ms at a frequency of 1 Hz. The power consumption was recorded as less than a few μW. Moreover, a reliability test showed stability over 10 000 loading-unloading cycles. Additionally, linear regression was performed in terms of temperature, which showed no significant variations, and there were no significant current variations with humidity. The patchable ion channel pressure sensors were then used to detect blood pressure/pulse in humans, and different signals were clearly observed for each person. Additionally, modified ion channel pressure sensors detected complex motions including pressing and folding in a high-pressure range (10-20 kPa).

An Insertable Passive LC Pressure Sensor Based on an Alumina Ceramic for In Situ Pressure Sensing in High-Temperature Environments.

PubMed

Xiong, Jijun; Li, Chen; Jia, Pinggang; Chen, Xiaoyong; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Tan, Qiulin

2015-08-31

Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively.

Wireless measurement of tire pressure with passive quartz sensors

NASA Astrophysics Data System (ADS)

Grossmann, Rainer

1999-05-01

The air pressure in the tires of a vehicle affects its stability, handling and braking and may contribute to causing an accident. Under-inflated tires increase fuel consumption. Existing measurement systems for the monitoring of the tire pressure use active sensors which need a battery or bulky energy transmission. This work shows a new approach: Quartz crystals as sensors can operate passively, without energy supply, by giving an echo to a stimulus pulse. Strain influences the otherwise extremely stable natural frequency of a quartz crystal which is therefore ideally suited for pressure measurements. As the natural frequency lies in the Megahertz range, stimulation and response can be transmitted by a pair of small antennas. A wireless measurement system has been built with excellent accuracy and resolution and a lightweight sensor which is very reliable and in principle maintenance-free.

High Temperature Capacitive Pressure Sensor Employing a SiC Based Ring Oscillator

NASA Technical Reports Server (NTRS)

Meredith, Roger D.; Neudeck, Philip G.; Ponchak, George E.; Beheim, Glenn M.; Scardelletti, Maximilian; Jordan, Jennifer L.; Chen, Liang-Yu; Spry, David J.; Krawowski, Michael J.; Hunter, Gary W.

2011-01-01

In an effort to develop harsh environment electronic and sensor technologies for aircraft engine safety and monitoring, we have used capacitive-based pressure sensors to shift the frequency of a SiC-electronics-based oscillator to produce a pressure-indicating signal that can be readily transmitted, e.g. wirelessly, to a receiver located in a more benign environment. Our efforts target 500 C, a temperature well above normal operating conditions of commercial circuits but within areas of interest in aerospace engines, deep mining applications and for future missions to the Venus atmosphere. This paper reports for the first time a ring oscillator circuit integrated with a capacitive pressure sensor, both operating at 500 C. This demonstration represents a significant step towards a wireless pressure sensor that can operate at 500 C and confirms the viability of 500 C electronic sensor systems.

Pressure sensor for high-temperature liquids

DOEpatents

Forster, George A.

1978-01-01

A pressure sensor for use in measuring pressures in liquid at high temperatures, especially such as liquid sodium or liquid potassium, comprises a soft diaphragm in contact with the liquid. The soft diaphragm is coupled mechanically to a stiff diaphragm. Pressure is measured by measuring the displacment of both diaphragms, typically by measuring the capacitance between the stiff diaphragm and a fixed plate when the stiff diaphragm is deflected in response to the measured pressure through mechanical coupling from the soft diaphragm. Absolute calibration is achieved by admitting gas under pressure to the region between diaphragms and to the region between the stiff diaphragm and the fixed plate, breaking the coupling between the soft and stiff diaphragms. The apparatus can be calibrated rapidly and absolutely.

Fabrication and Performance of MEMS-Based Pressure Sensor Packages Using Patterned Ultra-Thick Photoresists

PubMed Central

Chen, Lung-Tai; Chang, Jin-Sheng; Hsu, Chung-Yi; Cheng, Wood-Hi

2009-01-01

A novel plastic packaging of a piezoresistive pressure sensor using a patterned ultra-thick photoresist is experimentally and theoretically investigated. Two pressure sensor packages of the sacrifice-replacement and dam-ring type were used in this study. The characteristics of the packaged pressure sensors were investigated by using a finite-element (FE) model and experimental measurements. The results show that the thermal signal drift of the packaged pressure sensor with a small sensing-channel opening or with a thin silicon membrane for the dam-ring approach had a high packaging induced thermal stress, leading to a high temperature coefficient of span (TCO) response of −0.19% span/°C. The results also show that the thermal signal drift of the packaged pressure sensors with a large sensing-channel opening for sacrifice-replacement approach significantly reduced packaging induced thermal stress, and hence a low TCO response of −0.065% span/°C. However, the packaged pressure sensors of both the sacrifice-replacement and dam-ring type still met the specification −0.2% span/°C of the unpackaged pressure sensor. In addition, the size of proposed packages was 4 × 4 × 1.5 mm3 which was about seven times less than the commercialized packages. With the same packaging requirement, the proposed packaging approaches may provide an adequate solution for use in other open-cavity sensors, such as gas sensors, image sensors, and humidity sensors. PMID:22454580

Review of recent developments and applications in low-pressure (vacuum outlet) gas chromatography

USDA-ARS?s Scientific Manuscript database

The concept of low pressure (LP) vacuum outlet gas chromatography (GC) was introduced more than 50 years ago, but it was not until the 2000s that its theoretical applicability to fast analysis of GC-amenable chemicals was realized. In practice, LPGC is implemented by placing the outlet of a short, ...

An Insertable Passive LC Pressure Sensor Based on an Alumina Ceramic for In Situ Pressure Sensing in High-Temperature Environments

PubMed Central

Xiong, Jijun; Li, Chen; Jia, Pinggang; Chen, Xiaoyong; Zhang, Wendong; Liu, Jun; Xue, Chenyang; Tan, Qiulin

2015-01-01

Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively. PMID:26334279

One-Dimensional Contact Mode Interdigitated Center of Pressure Sensor (CMIPS)

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Kang, Jinho; Park, Cheol; Harrison, Joycelyn S.; Guerreiro, Nelson M.; Hubbard, James E.

2009-01-01

A one dimensional contact mode interdigitated center of pressure sensor (CMIPS) has been developed. The experimental study demonstrated that the CMIPS has the capability to measure the overall pressure as well as the center of pressure in one dimension, simultaneously. A theoretical model for the CMIPS is established here based on the equivalent circuit of the configuration of the CMIPS as well as the material properties of the sensor. The experimental results match well with theoretical modeling predictions. A system mapped with two or more pieces of the CMIPS can be used to obtain information from the pressure distribution in multi-dimensions.

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor.

PubMed

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Li, Wangwang; Zhang, Diya; Xiong, Jijun

2016-07-22

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations.

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor

PubMed Central

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Li, Wangwang; Zhang, Diya; Xiong, Jijun

2016-01-01

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations. PMID:27455271

Fabrications and Performance of Wireless LC Pressure Sensors through LTCC Technology.

PubMed

Lin, Lin; Ma, Mingsheng; Zhang, Faqiang; Liu, Feng; Liu, Zhifu; Li, Yongxiang

2018-01-25

This paper presents a kind of passive wireless pressure sensor comprised of a planar spiral inductor and a cavity parallel plate capacitor fabricated through low-temperature co-fired ceramic (LTCC) technology. The LTCC material with a low Young's modulus of ~65 GPa prepared by our laboratory was used to obtain high sensitivity. A three-step lamination process was applied to construct a high quality cavity structure without using any sacrificial materials. The effects of the thickness of the sensing membranes on the sensitivity and detection range of the pressure sensors were investigated. The sensor with a 148 μm sensing membrane showed the highest sensitivity of 3.76 kHz/kPa, and the sensor with a 432 μm sensing membrane presented a high detection limit of 2660 kPa. The tunable sensitivity and detection limit of the wireless pressure sensors can meet the requirements of different scenes.

Alumina ceramic based high-temperature performance of wireless passive pressure sensor

NASA Astrophysics Data System (ADS)

Wang, Bo; Wu, Guozhu; Guo, Tao; Tan, Qiulin

2016-12-01

A wireless passive pressure sensor equivalent to inductive-capacitive (LC) resonance circuit and based on alumina ceramic is fabricated by using high temperature sintering ceramic and post-fire metallization processes. Cylindrical copper spiral reader antenna and insulation layer are designed to realize the wireless measurement for the sensor in high temperature environment. The high temperature performance of the sensor is analyzed and discussed by studying the phase-frequency and amplitude-frequency characteristics of reader antenna. The average frequency change of sensor is 0.68 kHz/°C when the temperature changes from 27°C to 700°C and the relative change of twice measurements is 2.12%, with high characteristic of repeatability. The study of temperature-drift characteristic of pressure sensor in high temperature environment lays a good basis for the temperature compensation methods and insures the pressure signal readout accurately.

Fluid leakage detector for vacuum applications

NASA Technical Reports Server (NTRS)

Nguyen, Bich Ngoc (Inventor); Farkas, Tibor (Inventor); Kim, Brian Byungkyu (Inventor)

2002-01-01

A leak detection system for use with a fluid conducting system in a vacuum environment, such as space, is described. The system preferably includes a mesh-like member substantially disposed about the fluid conducting system, and at least one sensor disposed within the mesh-like member. The sensor is capable of detecting a decrease in temperature of the mesh-like member when a leak condition causes the fluid of the fluid conducting system to freeze when exposed to the vacuum environment. Additionally, a signal processor in preferably in communication with the sensor. The sensor transmits an electrical signal to the signal processor such that the signal processor is capable of indicating the location of the fluid leak in the fluid conducting system.

A microfluidic circulatory system integrated with capillary-assisted pressure sensors.

PubMed

Chen, Yangfan; Chan, Ho Nam; Michael, Sean A; Shen, Yusheng; Chen, Yin; Tian, Qian; Huang, Lu; Wu, Hongkai

2017-02-14

The human circulatory system comprises a complex network of blood vessels interconnecting biologically relevant organs and a heart driving blood recirculation throughout this system. Recreating this system in vitro would act as a bridge between organ-on-a-chip and "body-on-a-chip" and advance the development of in vitro models. Here, we present a microfluidic circulatory system integrated with an on-chip pressure sensor to closely mimic human systemic circulation in vitro. A cardiac-like on-chip pumping system is incorporated in the device. It consists of four pumping units and passive check valves, which mimic the four heart chambers and heart valves, respectively. Each pumping unit is independently controlled with adjustable pressure and pump rate, enabling users to control the mimicked blood pressure and heartbeat rate within the device. A check valve is located downstream of each pumping unit to prevent backward leakage. Pulsatile and unidirectional flow can be generated to recirculate within the device by programming the four pumping units. We also report an on-chip capillary-assisted pressure sensor to monitor the pressure inside the device. One end of the capillary was placed in the measurement region, while the other end was sealed. Time-dependent pressure changes were measured by recording the movement of the liquid-gas interface in the capillary and calculating the pressure using the ideal gas law. The sensor covered the physiologically relevant blood pressure range found in humans (0-142.5 mmHg) and could respond to 0.2 s actuation time. With the aid of the sensor, the pressure inside the device could be adjusted to the desired range. As a proof of concept, human normal left ventricular and arterial pressure profiles were mimicked inside this device. Human umbilical vein endothelial cells (HUVECs) were cultured on chip and cells can respond to mechanical forces generated by arterial-like flow patterns.

Thin film devices used as oxygen partial pressure sensors

NASA Technical Reports Server (NTRS)

Canady, K. S.; Wortman, J. J.

1970-01-01

Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

FLUID PRESSURE AND CAM OPERATED VACUUM VALVE

DOEpatents

Batzer, T.H.

1963-11-26

An ultra-high vacuum valve that is bakable, reusable, and capable of being quickly opened and closed is described. A translationally movable valve gate having an annular ridge is adapted to contact an annular soft metal gasket disposed at the valve seat such that the soft metal gasket extends beyond the annular ridge on all sides. The valve gate is closed, by first laterally aligning the valve gate with the valve seat and then bringing the valve gate and valve seat into seating contact by the translational movement of a ramp-like wedging means that engages similar ramp-like stractures at the base of the valve gate to force the valve gate into essentially pressureless contact with the annular soft metal gasket. This gasket is then pressurized from beneath by a fluid thereby effecting a vacuura tight seal between the gasket and the ridge. (AEC)

The Responsivity of a Miniaturized Passive Implantable Wireless Pressure Sensor.

PubMed

Jiang, Hao; Lan, Di; Goldman, Ken; Etemadi, Mozziyar; Shahnasser, Hamid; Roy, Shuvo

2011-01-01

A miniature batteryless implantable wireless pressure sensor that can be used deep inside the body is desired by the medical community. MEMS technology makes it possible to achieve high responsivity that directly determines the operating distance between a miniature implanted sensor and the external RF probe, while providing the read-out. In this paper, for the first time, an analytical expression of the system responsivity versus the sensor design is derived using an equivalent circuit model. Also, the integration of micro-coil inductors and pressure sensitive capacitors on a single silicon chip using MEMS fabrication techniques is demonstrated. Further, the derived analytical design theory is validated by the measured responsivity of these sensors.

Test of FBG sensors for monitoring high pressure pipes

NASA Astrophysics Data System (ADS)

Paolozzi, Antonio; Paris, Claudio; Vendittozzi, Cristian; Felli, Ferdinando; Mongelli, Marialuisa; De Canio, Gerardo; Colucci, Alessandro; Asanuma, Hiroshi

2017-04-01

Fibre Bragg Grating (FBG) sensors are increasingly being used on a wide range of civil, industrial and aerospace structures. The sensors are created inside optical fibres (usually standard telecommunication fibres); the optical fibres technology allows to install the sensors on structures working in harsh environments, since the materials are almost insensitive to corrosion, the monitoring system can be positioned far away from the sensors without sensible signal losses, and there is no risk of electric discharge. FBG sensors can be used to create strain gages, thermometers or accelerometers, depending on the coating on the grating, on the way the grating is fixed to the structure, and on the presence of a specifically designed interface that can act as a transducer. This paper describes a test of several different FBG sensors to monitor an high pressure pipe that feeds the hydraulic actuators of a 6 degrees-of-freedom shaking table at the ENEA Casaccia research centre. A bare FBG sensor and a copper coated FBG sensor have been glued on the pipe. A third sensor has been mounted on a special interface to amplify the vibrations; this last sensor can be placed on the steel pipe by a magnetic mounting system, that also allows the its removal. All the sensor are placed parallel to the axis of the pipe. The analysis of the data recorded when the shaking table is operated will allow to determine which kind of sensor is best suited for structural monitoring of high pressure pipelines.

Rough-Surface-Enabled Capacitive Pressure Sensors with 3D Touch Capability.

PubMed

Lee, Kilsoo; Lee, Jaehong; Kim, Gwangmook; Kim, Youngjae; Kang, Subin; Cho, Sungjun; Kim, SeulGee; Kim, Jae-Kang; Lee, Wooyoung; Kim, Dae-Eun; Kang, Shinill; Kim, DaeEun; Lee, Taeyoon; Shim, Wooyoung

2017-11-01

Fabrication strategies that pursue "simplicity" for the production process and "functionality" for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper-based pressure sensors are integrated into a fully functional 3D touch-pad device, which is a step toward the realization of omnipresent electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of All-SiC Fiber-Optic Pressure Sensors for High-Temperature Applications.

PubMed

Jiang, Yonggang; Li, Jian; Zhou, Zhiwen; Jiang, Xinggang; Zhang, Deyuan

2016-10-17

Single-crystal silicon carbide (SiC)-based pressure sensors can be used in harsh environments, as they exhibit stable mechanical and electrical properties at elevated temperatures. A fiber-optic pressure sensor with an all-SiC sensor head was fabricated and is herein proposed. SiC sensor diaphragms were fabricated via an ultrasonic vibration mill-grinding (UVMG) method, which resulted in a small grinding force and low surface roughness. The sensor head was formed by hermetically bonding two layers of SiC using a nickel diffusion bonding method. The pressure sensor illustrated a good linearity in the range of 0.1-0.9 MPa, with a resolution of 0.27% F.S. (full scale) at room temperature.

Improvement of a sensor unit for wrist blood pressure monitoring system

NASA Astrophysics Data System (ADS)

Koo, Sangjun; Kwon, Jongwon; Park, Yongman; Ayuzenara, Odgerel; Kim, Hiesik

2007-12-01

A blood pressure sensor unit for ubiquitous healthcare monitoring was newly developed. The digital wrist band-type blood pressure devices for home are popular already in the market. It is useful for checking blood pressure level at home and control of hypertension. Especially, it is very essential home device to check the health condition of blood circulation disease. Nowadays many product types are available. But the measurement of blood pressure is not accurate enough compared with the mechanical type. It needs to be upgraded to assure the precise health data enough to use in the hospital. The structure, feature and output signal of capacitor type pressure sensors are analyzed. An improved design of capacitor sensor is suggested. It shows more precise health data after use on a wrist band type health unit. They can be applied for remote u-health medical service.

Multi-channel electronically scanned cryogenic pressure sensor

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Hopson, Purnell, Jr. (Inventor); Kruse, Nancy M. H. (Inventor)

1995-01-01

A miniature, multi-channel, electronically scanned pressure measuring device uses electrostatically bonded silicon dies in a multielement array. These dies are bonded at specific sites on a glass, prepatterned substrate. Thermal data is multiplexed and recorded on each individual pressure measuring diaphragm. The device functions in a cryogenic environment without the need of heaters to keep the sensor at constant temperatures.

Using smartphone pressure sensors to measure vertical velocities of elevators, stairways, and drones

NASA Astrophysics Data System (ADS)

Monteiro, Martín; Martí, Arturo C.

2017-01-01

We measure the vertical velocities of elevators, pedestrians climbing stairs, and drones (flying unmanned aerial vehicles), by means of smartphone pressure sensors. The barometric pressure obtained with the smartphone is related to the altitude of the device via the hydrostatic approximation. From the altitude values, vertical velocities are derived. The approximation considered is valid in the first hundred meters of the inner layers of the atmosphere. In addition to pressure, acceleration values were also recorded using the built-in accelerometer. Numerical integration was performed, obtaining both vertical velocity and altitude. We show that data obtained using the pressure sensor is significantly less noisy than that obtained using the accelerometer. Error accumulation is also evident in the numerical integration of the acceleration values. In the proposed experiments, the pressure sensor also outperforms GPS, because this sensor does not receive satellite signals indoors and, in general, the operating frequency is considerably lower than that of the pressure sensor. In the cases in which it is possible, comparison with reference values taken from the architectural plans of buildings validates the results obtained using the pressure sensor. This proposal is ideally performed as an external or outreach activity with students to gain insight about fundamental questions in mechanics, fluids, and thermodynamics.

Optical fibre pressure and temperature sensor system designed for urodynamic applications

NASA Astrophysics Data System (ADS)

Duraibabu, Dineshbabu; Kelly, Niall; Poeggel, Sven; Flood, Hugh; Yuan, Hongwei; Dooly, Gerard; McGrath, Deirdre; Tosi, Daniele; Lewis, Elfed; Leen, Gabriel

2016-05-01

This paper presents an optical fibre pressure and temperature sensor (OFPTS) system, which is adapted for use as a urodynamic pressure measurement system (UPS) for differential pressure measurement with temperature compensation. The OFTPS is based on a Fabry Perot interferometer (FPI), which acts as a pressure sensor and includes an embedded fibre Bragg grating (FBG) for temperature measurement. The sensor system is evaluated in a lower urinary tract (LUT) simulator, which simulates the bladder, rectum and detrusor muscle. The system was benchmarked against a commercially available urodynamic system, at the University Hospital Limerick (UHL) Urology Clinic. Both systems demonstrate a high correlation with a relative pressure variation of less than +/-2.8cmH2O for abdominal and +/-4cmH2O for vesical pressure. The repetitive measurement of the OFPTS system in the LUT simulator against the commercial system demonstrated the high repeatability. Furthermore, the low fabrication cost makes the OFPTS a potentially interesting instrument for urodynamic and other medical applications.

Mixed Traffic Information Collection System based on Pressure Sensor

NASA Astrophysics Data System (ADS)

Liao, Wenzhe; Liu, Mingsheng; Meng, Qingli

The traffic information collection is the base of Intelligent Traffic.At present, there exist mixed traffic situation in urban road in China. This paper researched and implemented a system through collecting the vehicle and bicycle mixed traffic flow parameters based on pressure sensor. According to information collection requirements, we selected pressure sensor, designed the data collection, storage and other hardware circuitries and information processing software. The experiment shows that the system can meet the demand of traffic information collection in the actual.

A flexible touch-pressure sensor array with wireless transmission system for robotic skin

NASA Astrophysics Data System (ADS)

Huang, Ying; Fang, Ding; Wu, Can; Wang, Weihua; Guo, Xiaohui; Liu, Ping

2016-06-01

Human skin contains multiple receptors and is able to sense various stimuli such as temperature, touch, pressure, and deformation, with high sensitivity and resolution. The development of skin-like sensors capable of sensing these stimuli is of great importance for various applications such as robots, touch detection, temperature monitoring, and strain gauges. Great efforts have been made to develop high performance touch sensor and pressure sensor. Compared with general sensor, the touch-pressure sensor which is reported in this paper not only can measure large pressure but also has a high resolution in the small range so that it can feel slight touch. The sensor has a vertical structure. The upper layer is made of silicone rubber as the capacitive layer and the lower layer employs multiwall carbon nanotubes and carbon black filled silicone rubber as the resistive layer. The electrodes are made by conductive silver adhesives. In addition, the electrodes are connected to the pads on the top surface of the flexible printed circuit board by enamelled wires which made it easier to fabricate sensor array. The resolution of the touch-pressure sensor in the range of 0-10 N and 10-100 N are 0.1 N and 1 N, respectively. The experimental data of the sensor are sent by ZigBee wireless technology which reduces the complexity of the wiring and provides a convenient way to apply and maintain the sensor array.

A flexible touch-pressure sensor array with wireless transmission system for robotic skin.

PubMed

Huang, Ying; Fang, Ding; Wu, Can; Wang, Weihua; Guo, Xiaohui; Liu, Ping

2016-06-01

Human skin contains multiple receptors and is able to sense various stimuli such as temperature, touch, pressure, and deformation, with high sensitivity and resolution. The development of skin-like sensors capable of sensing these stimuli is of great importance for various applications such as robots, touch detection, temperature monitoring, and strain gauges. Great efforts have been made to develop high performance touch sensor and pressure sensor. Compared with general sensor, the touch-pressure sensor which is reported in this paper not only can measure large pressure but also has a high resolution in the small range so that it can feel slight touch. The sensor has a vertical structure. The upper layer is made of silicone rubber as the capacitive layer and the lower layer employs multiwall carbon nanotubes and carbon black filled silicone rubber as the resistive layer. The electrodes are made by conductive silver adhesives. In addition, the electrodes are connected to the pads on the top surface of the flexible printed circuit board by enamelled wires which made it easier to fabricate sensor array. The resolution of the touch-pressure sensor in the range of 0-10 N and 10-100 N are 0.1 N and 1 N, respectively. The experimental data of the sensor are sent by ZigBee wireless technology which reduces the complexity of the wiring and provides a convenient way to apply and maintain the sensor array.

NSLS II Vacuum System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferreira, M.; Doom, L.; Hseuh, H.

2009-09-13

National Synchrotron Light Source II, being constructed at Brookhaven, is a 3-GeV, 500 mA, 3rd generation synchrotron radiation facility with ultra low emittance electron beams. The storage ring vacuum system has a circumference of 792 m and consists of over 250 vacuum chambers with a simulated average operating pressure of less than 1 x 10{sup -9} mbar. A summary of the update design of the vacuum system including girder supports of the chambers, gauges, vacuum pumps, bellows, beam position monitors and simulation of the average pressure will be shown. A brief description of the techniques and procedures for cleaning andmore » mounting the chambers are given.« less

FBG based high sensitive pressure sensor and its low-cost interrogation system with enhanced resolution

NASA Astrophysics Data System (ADS)

Pachava, Vengal Rao; Kamineni, Srimannarayana; Madhuvarasu, Sai Shankar; Putha, Kishore; Mamidi, Venkata Reddy

2015-12-01

A fiber Bragg grating (FBG) pressure sensor with high sensitivity and resolution has been designed and demonstrated. The sensor is configured by firmly fixing the FBG with a metal bellows structure. The sensor works by means of measuring the Bragg wavelength shift of the FBG with respect to pressure change. From the experimental results, the pressure sensitivity of the sensor is found to be 90.6 pm/psi, which is approximately 4000 times as that of a bare fiber Bragg grating. A very good linearity of 99.86% is observed between the Bragg wavelength of the FBG and applied pressure. The designed sensor shows good repeatability with a negligible hysteresis error of ± 0.29 psi. A low-cost interrogation system that includes a long period grating (LPG) and a photodiode (PD) accompanied with simple electronic circuitry is demonstrated for the FBG sensor, which enables the sensor to attain high resolution of up to 0.025 psi. Thermal-strain cross sensitivity of the FBG pressure sensor is compensated using a reference FBG temperature sensor. The designed sensor can be used for liquid level, specific gravity, and static/dynamic low pressure measurement applications.

A Wind Tunnel Study on the Mars Pathfinder (MPF) Lander Descent Pressure Sensor

NASA Technical Reports Server (NTRS)

Soriano, J. Francisco; Coquilla, Rachael V.; Wilson, Gregory R.; Seiff, Alvin; Rivell, Tomas

2001-01-01

The primary focus of this study was to determine the accuracy of the Mars Pathfinder lander local pressure readings in accordance with the actual ambient atmospheric pressures of Mars during parachute descent. In order to obtain good measurements, the plane of the lander pressure sensor opening should ideally be situated so that it is parallel to the freestream. However, due to two unfavorable conditions, the sensor was positioned in locations where correction factors are required. One of these disadvantages is due to the fact that the parachute attachment point rotated the lander's center of gravity forcing the location of the pressure sensor opening to be off tangent to the freestream. The second and most troublesome factor was that the lander descends with slight oscillations that could vary the amplitude of the sensor readings. In order to accurately map the correction factors required at each sensor position, an experiment simulating the lander descent was conducted in the Martian Surface Wind Tunnel at NASA Ames Research Center. Using a 115 scale model at Earth ambient pressures, the test settings provided the necessary Reynolds number conditions in which the actual lander was possibly subjected to during the descent. In the analysis and results of this experiment, the readings from the lander sensor were converted to the form of pressure coefficients. With a contour map of pressure coefficients at each lander oscillatory position, this report will provide a guideline to determine the correction factors required for the Mars Pathfinder lander descent pressure sensor readings.

Optical fiber pressure and acceleration sensor fabricated on a fiber endface

DOEpatents

Zhu, Yizheng; Wang, Xingwei; Xu, Juncheng; Wang, Anbo

2006-05-30

A fiber optic sensor has a hollow tube bonded to the endface of an optical fiber, and a diaphragm bonded to the hollow tube. The fiber endface and diaphragm comprise an etalon cavity. The length of the etalon cavity changes when applied pressure or acceleration flexes the diaphragm. The entire structure can be made of fused silica. The fiber, tube, and diaphragm can be bonded with a fusion splice. The present sensor is particularly well suited for measuring pressure or acceleration in high temperature, high pressure and corrosive environments (e.g., oil well downholes and jet engines). The present sensors are also suitable for use in biological and medical applications.

Vacuum Radiance-Temperature Standard Facility for Infrared Remote Sensing at NIM

NASA Astrophysics Data System (ADS)

Hao, X. P.; Song, J.; Xu, M.; Sun, J. P.; Gong, L. Y.; Yuan, Z. D.; Lu, X. F.

2018-06-01

As infrared remote sensors are very important parts of Earth observation satellites, they must be calibrated based on the radiance temperature of a blackbody in a vacuum chamber prior to launch. The uncertainty of such temperature is thus an essential component of the sensors' uncertainty. This paper describes the vacuum radiance-temperature standard facility (VRTSF) at the National Institute of Metrology of China, which will serve to calibrate infrared remote sensors on Chinese meteorological satellites. The VRTSF can be used to calibrate vacuum blackbody radiance temperature, including those used to calibrate infrared remote sensors. The components of the VRTSF are described in this paper, including the VMTBB, the LNBB, the FTIR spectrometer, the reduced-background optical system, the vacuum chamber used to calibrate customers' blackbody, the vacuum-pumping system and the liquid-nitrogen-support system. The experimental methods and results are expounded. The uncertainty of the radiance temperature of VMTBB is 0.026 °C at 30 °C over 10 μm.

Enhanced performance of microfluidic soft pressure sensors with embedded solid microspheres

NASA Astrophysics Data System (ADS)

Shin, Hee-Sup; Ryu, Jaiyoung; Majidi, Carmel; Park, Yong-Lae

2016-02-01

The cross-sectional geometry of an embedded microchannel influences the electromechanical response of a soft microfluidic sensor to applied surface pressure. When a pressure is exerted on the surface of the sensor deforming the soft structure, the cross-sectional area of the embedded channel filled with a conductive fluid decreases, increasing the channel’s electrical resistance. This electromechanical coupling can be tuned by adding solid microspheres into the channel. In order to determine the influence of microspheres, we use both analytic and computational methods to predict the pressure responses of soft microfluidic sensors with two different channel cross-sections: a square and an equilateral triangular. The analytical models were derived from contact mechanics in which microspheres were regarded as spherical indenters, and finite element analysis (FEA) was used for simulation. For experimental validation, sensor samples with the two different channel cross-sections were prepared and tested. For comparison, the sensor samples were tested both with and without microspheres. All three results from the analytical models, the FEA simulations, and the experiments showed reasonable agreement confirming that the multi-material soft structure significantly improved its pressure response in terms of both linearity and sensitivity. The embedded solid particles enhanced the performance of soft sensors while maintaining their flexible and stretchable mechanical characteristic. We also provide analytical and experimental analyses of hysteresis of microfluidic soft sensors considering a resistive force to the shape recovery of the polymer structure by the embedded viscous fluid.

Mimosa-inspired design of a flexible pressure sensor with touch sensitivity.

PubMed

Su, Bin; Gong, Shu; Ma, Zheng; Yap, Lim Wei; Cheng, Wenlong

2015-04-24

A bio-inspired flexible pressure sensor is generated with high sensitivity (50.17 kPa(-1)), quick responding time (<20 ms), and durable stability (negligible loading-unloading signal changes over 10 000 cycles). Notably, the key resource of surface microstructures upon sensor substrates results from the direct molding of natural mimosa leaves, presenting a simple, environment-friendly and easy scale-up fabrication process for these flexible pressure sensors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and characterization of bending and pressure sensors for a soft prosthetic hand

NASA Astrophysics Data System (ADS)

Rocha, Rui Pedro; Alhais Lopes, Pedro; de Almeida, Anibal T.; Tavakoli, Mahmoud; Majidi, Carmel

2018-03-01

We demonstrate fabrication, characterization, and implementation of ‘soft-matter’ pressure and bending sensors for a soft robotic hand. The elastomer-based sensors are embedded in a robot finger composed of a 3D printed endoskeleton and covered by an elastomeric skin. Two types of sensors are evaluated, resistive pressure sensors and capacitive pressure sensors. The sensor is fabricated entirely out of insulating and conductive rubber, the latter composed of polydimethylsiloxane (PDMS) elastomer embedded with a percolating network of structured carbon black (CB). The sensor-integrated fingers have a simple materials architecture, can be fabricated with standard rapid prototyping methods, and are inexpensive to produce. When incorporated into a robotic hand, the CB-PDMS sensors and PDMS carrier medium function as an ‘artificial skin’ for touch and bend detection. Results show improved response with a capacitive sensor architecture, which, unlike a resistive sensor, is robust to electromechanical hysteresis, creep, and drift in the CB-PDMS composite. The sensorized fingers are integrated in an anthropomorphic hand and results for a variety of grasping tasks are presented.

Fabrication of All-SiC Fiber-Optic Pressure Sensors for High-Temperature Applications

PubMed Central

Jiang, Yonggang; Li, Jian; Zhou, Zhiwen; Jiang, Xinggang; Zhang, Deyuan

2016-01-01

Single-crystal silicon carbide (SiC)-based pressure sensors can be used in harsh environments, as they exhibit stable mechanical and electrical properties at elevated temperatures. A fiber-optic pressure sensor with an all-SiC sensor head was fabricated and is herein proposed. SiC sensor diaphragms were fabricated via an ultrasonic vibration mill-grinding (UVMG) method, which resulted in a small grinding force and low surface roughness. The sensor head was formed by hermetically bonding two layers of SiC using a nickel diffusion bonding method. The pressure sensor illustrated a good linearity in the range of 0.1–0.9 MPa, with a resolution of 0.27% F.S. (full scale) at room temperature. PMID:27763494

Development, Fabrication, and Characterization of Hydrogel Based Piezoresistive Pressure Sensors with Perforated Diaphragms

PubMed Central

Orthner, M.P.; Buetefisch, Sebastian; Magda, J.; Rieth, L.W.; Solzbacher, F.

2010-01-01

Hydrogels have been demonstrated to swell in response to a number of external stimuli including pH, CO2, glucose, and ionic strength making them useful for detection of metabolic analytes. To measure hydrogel swelling pressure, we have fabricated and tested novel perforated diaphragm piezoresistive pressure sensor arrays that couple the pressure sensing diaphragm with a perforated semi-permeable membrane. The 2×2 arrays measure approximately 3 × 5 mm2 and consist of four square sensing diaphragms with widths of 1.0, 1.25, and 1.5 mm used to measure full scale pressures of 50, 25, and 5 kPa, respectively. An optimized geometry of micro pores was etched in silicon diaphragm to allow analyte diffusion into the sensor cavity where the hydrogel material is located. The 14-step front side wafer process was carried out by a commercial foundry service (MSF, Frankfurt (Oder), Germany) and diaphragm pores were created using combination of potassium hydroxide (KOH) etching and deep reactive ion etching (DRIE). Sensor characterization was performed (without the use of hydrogels) using a custom bulge testing apparatus that simultaneously measured deflection, pressure, and electrical output. Test results are used to quantify the sensor sensitivity and demonstrate proof-of-concept. Simulations showed that the sensitivity was slightly improved for the perforated diaphragm designs while empirical electrical characterization showed that the perforated diaphragm sensors were slightly less sensitive than solid diaphragm sensors. This discrepancy is believed to be due to the influence of compressive stress found within passivation layers and poor etching uniformity. The new perforated diaphragm sensors were fully functional with sensitivities ranging from 23 to 252 μV/V-kPa (FSO= 5 to 80mV), and show a higher nonlinearity at elevated pressures than identical sensors with solid diaphragms. Sensors (1.5×1.5 mm2) with perforated diaphragms (pores=40 μm) have a nonlinearity of

Simulation and optimization of silicon-on-sapphire pressure sensor

NASA Astrophysics Data System (ADS)

Kulesh, N. A.; Kudyukov, E. V.; Balymov, K. G.; Beloyshov, A. A.

2017-09-01

In this paper, finite element analysis software COMSOL Multiphysics was used to simulate the performance of silicon-on-sapphire piezoresistive pressure sensor, aiming to elaborate a flexible model suitable for further optimization and customization of the currently produced pressure sensors. The base model was built around the cylindrical pressure cell made of titanium alloy having a circular diaphragm with monocrystalline sapphire layer attached. The monocrystalline piezoresistive elements were placed on top of the double-layer diaphragm and electrically connected to form the Wheatstone bridge. Verification of the model and parametric study included three main areas: geometrical parameters of the cell, position of the elements on the diaphragm, and operation at elevated temperature. Optimization of the cell geometry included variation of bossed titanium diaphragm parameters as well as rounding-off radiuses near the edges of the diaphragm. Influence of the temperature was considered separately for thermal expansion of the mechanical components and for the changes of electrical and piezoresistive properties of the piezoresistive elements. In conclusion, the simulation results were compared to the experimental data obtained for three different constructions of the commercial pressure sensors produced by SPA of Automatics named after Academician N.A. Semikhatov.

Fabrication and Characteristics of an nc-Si/c-Si Heterojunction MOSFETs Pressure Sensor

PubMed Central

Zhao, Xiaofeng; Wen, Dianzhong; Li, Gang

2012-01-01

A novel nc-Si/c-Si heterojunction MOSFETs pressure sensor is proposed in this paper, with four p-MOSFETs with nc-Si/c-Si heterojunction as source and drain. The four p-MOSFETs are designed and fabricated on a square silicon membrane by CMOS process and MEMS technology where channel resistances of the four nc-Si/c-Si heterojunction MOSFETs form a Wheatstone bridge. When the additional pressure is P, the nc-Si/c-Si heterojunction MOSFETs pressure sensor can measure this additional pressure P. The experimental results show that when the supply voltage is 3 V, length-width (L:W) ratio is 2:1, and the silicon membrane thickness is 75 μm, the full scale output voltage of the pressure sensor is 15.50 mV at room temperature, and pressure sensitivity is 0.097 mV/kPa. When the supply voltage and L:W ratio are the same as the above, and the silicon membrane thickness is 45 μm, the full scale output voltage is 43.05 mV, and pressure sensitivity is 2.153 mV/kPa. Therefore, the sensor has higher sensitivity and good temperature characteristics compared to the traditional piezoresistive pressure sensor. PMID:22778646

Wireless Prototype Based on Pressure and Bending Sensors for Measuring Gate Quality

PubMed Central

Grenez, Florent; Villarejo, María Viqueira; Zapirain, Begoña García; Zorrilla, Amaia Méndez

2013-01-01

This paper presents a technological solution based on sensors controlled remotely in order to monitor, track and evaluate the gait quality in people with or without associated pathology. Special hardware simulating a shoe was developed, which consists of three pressure sensors, two bending sensors, an Arduino mini and a Bluetooth module. The obtained signals are digitally processed, calculating the standard deviation and establishing thresholds obtained empirically. A group of users was chosen with the aim of executing two modalities: natural walking and dragging the left foot. The gait was parameterized with the following variables: as far as pressure sensors are concerned, one pressure sensor under the first metatarsal (right sensor), another one under the fifth metatarsal (left) and a third one under the heel were placed. With respect to bending sensors, one bending sensor was placed for the ankle movement and another one for the foot sole. The obtained results show a rate accuracy oscillating between 85% (right sensor) and 100% (heel and bending sensors). Therefore, the developed prototype is able to differentiate between healthy gait and pathological gait, and it will be used as the base of a more complex and integral technological solution, which is being developed currently. PMID:23899935

Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application.

PubMed

Liang, Hao; Jia, Pinggang; Liu, Jia; Fang, Guocheng; Li, Zhe; Hong, Yingping; Liang, Ting; Xiong, Jijun

2018-03-28

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The FP cavity length between the ends of the SMF and HST changes with the gas density. Using temperature decoupling method to improve the accuracy of the pressure sensor in high temperature environments. An experimental system for measuring the pressure under different temperatures was established to verify the performance of the sensor. The pressure sensitivity of the FP gas pressure sensor is 4.28 nm/MPa with a high linear pressure response over the range of 0.1-0.7 MPa, and the temperature sensitivity is 14.8 pm/°C under the range of 20-800 °C. The sensor has less than 1.5% non-linearity at different temperatures by using temperature decoupling method. The simple fabrication and low-cost will help sensor to maintain the excellent features required by pressure measurement in high temperature applications.

Tekscan pressure sensor output changes in the presence of liquid exposure.

PubMed

Jansson, Kyle S; Michalski, Max P; Smith, Sean D; LaPrade, Robert F; Wijdicks, Coen A

2013-02-01

The purpose of the study was to evaluate the load output of a pressure sensor in the presence of liquid saturation in a controlled environment. We hypothesized that a calibrated pressure sensor would provide diminishing load outputs over time in controlled environments of both humidified air and while submerged in saline and the sensors would reach a steady state output once saturated. A consistent compressive load was repeatedly applied to pressure sensors over time (Model 4000, Tekscan, Inc., South Boston, MA) with a tensile testing machine (Instron ElectroPuls E10000, Norwood, MA). All sensors were initially calibrated in a dry environment and were tested in three groups: humid air, submerged in 0.9% saline solution, and dry. Linear regression of load output over time for the pressure sensors exposed to humidity and submerged showed a 4.6% and 4.7% decline in load output each hour for the initial 6h, respectively (β=-0.046, 95% CI: [-0.053 to -0.039]; p<0.001) (β=-0.047, 95% CI: [-0.053 to -0.042; p<0.001). Tests after 72 h of exposure had linear regression decline in load output over time of 0.40% and 0.47% per hour for humidified and submerged sensors, respectively (β=-0.004, 95% CI: [-0.006 to -0.003]; p<0.001) (β=-0.047, 95% CI: [-0.053 to -0.042]; p<0.001). Because outcomes in biomedical research can affect clinical practices and treatments, the diminishing load output of the sensor in the presence of liquids should be accounted for. We recommend soaking sensors for more than 48 h prior to testing in a moist environment. Copyright © 2012 Elsevier Ltd. All rights reserved.

Fabrication and characterization of 3C-silicon carbide micro sensor for wireless blood pressure measurements

NASA Astrophysics Data System (ADS)

Basak, Nupur

A potentially implantable single crystal 3C-SiC pressure sensor for blood pressure measurement was designed, simulated, fabricated, characterized and optimized. This research uses a single crystal 3C-SiC, for the first time, to demonstrate its application as a blood pressure measurement sensor. The sensor, which uses the epitaxial grown 3C-SiC membrane to measure changes in pressure, is designed to be wireless, biocompatible and linear. The SiC material was chosen for its superior physical, chemical and mechanical properties; the capacitive sensor uses a 3C-SiC membrane as one of the electrodes; and, the sensor system is wireless for comfort and to allow for convenient reading of real-time pressure data (wireless communication is enabled by connecting the sensor parallel to a planar inductor). Together, the variable capacitive sensor and planar inductor create a pressure sensitive resonant circuit. The sensor system described above allows for implantation into a human patient's body, after which the planar inductor can be coupled with an external inductor to receive data for real-time blood pressure measurement. Electroplating, thick photo-resist characterization, RIE etching, oxidation, CVD, chemical mechanical polishing and wafer bonding were optimized during the process of fabricating the sensor system and, in addition to detailing the sensor system simulation and characterization; the optimized processes are detailed in the dissertation. This absolute pressure sensor is designed to function optimally within the human blood pressure range of 50-350mmHg. The layout and modeling of the sensor uses finite element analysis (FEA) software. The simulations for membrane deflection, stress analysis and electro-mechanical analysis are performed for 100 μm2 and 400μm2sensors. The membrane deflection-pressure, capacitance-pressure and resonant frequency-pressure graphs were obtained, and detailed in the dissertation, along with the planar inductor simulation for

Microelectromechanical system pressure sensor integrated onto optical fiber by anodic bonding.

PubMed

Saran, Anish; Abeysinghe, Don C; Boyd, Joseph T

2006-03-10

Optical microelectromechanical system pressure sensors based on the principle of Fabry-Perot interferometry have been developed and fabricated using the technique of silicon-to-silicon anodic bonding. The pressure sensor is then integrated onto an optical fiber by a novel technique of anodic bonding without use of any adhesives. In this anodic bonding technique we use ultrathin silicon of thickness 10 microm to bond the optical fiber to the sensor head. The ultrathin silicon plays the role of a stress-reducing layer, which helps the bonding of an optical fiber to silicon having conventional wafer thickness. The pressure-sensing membrane is formed by 8 microm thick ultrathin silicon acting as a membrane, thus eliminating the need for bulk silicon etching. The pressure sensor integrated onto an optical fiber is tested for static response, and experimental results indicate degradation in the fringe visibility of the Fabry-Perot interferometer. This effect was mainly due to divergent light rays from the fiber degrading the fringe visibility. This effect is demonstrated in brief by an analytical model.

Stretchable Dual-Capacitor Multi-Sensor for Touch-Curvature-Pressure-Strain Sensing.

PubMed

Jin, Hanbyul; Jung, Sungchul; Kim, Junhyung; Heo, Sanghyun; Lim, Jaeik; Park, Wonsang; Chu, Hye Yong; Bien, Franklin; Park, Kibog

2017-09-07

We introduce a new type of multi-functional capacitive sensor that can sense several different external stimuli. It is fabricated only with polydimethylsiloxane (PDMS) films and silver nanowire electrodes by using selective oxygen plasma treatment method without photolithography and etching processes. Differently from the conventional single-capacitor multi-functional sensors, our new multi-functional sensor is composed of two vertically-stacked capacitors (dual-capacitor). The unique dual-capacitor structure can detect the type and strength of external stimuli including curvature, pressure, strain, and touch with clear distinction, and it can also detect the surface-normal directionality of curvature, pressure, and touch. Meanwhile, the conventional single-capacitor sensor has ambiguity in distinguishing curvature and pressure and it can detect only the strength of external stimulus. The type, directionality, and strength of external stimulus can be determined based on the relative capacitance changes of the two stacked capacitors. Additionally, the logical flow reflected on a tree structure with its branches reaching the direction and strength of the corresponding external stimulus unambiguously is devised. This logical flow can be readily implemented in the sensor driving circuit if the dual-capacitor sensor is commercialized actually in the future.

Evaluation of eating and rumination behaviour in cows using a noseband pressure sensor

PubMed Central

2013-01-01

Background An automated technique for recording eating and rumination behaviour was evaluated in ten lactating Brown Swiss cows by comparing data obtained from a pressure sensor with data obtained via direct observation over a 24-hour period. The recording device involved a pressure sensor integrated in the noseband of a halter. The analysed variables included number and duration of individual rumination, eating and resting phases, total daily length of these phases and number of cuds chewed per day. Results Eating and rumination phases were readily differentiated based on characteristic pressure profiles. Chewing movements during rumination were regular and generated regular waveforms with uniform amplitudes, whereas eating generated irregular waveforms with variable amplitudes. There was complete or almost complete agreement and no significant differences between data obtained via direct observation and pressure sensor technique. Both methods yielded an average of 16 daily eating phases with a mean duration of 28.3 minutes. Total time spent eating was 445.0 minutes for direct observation and 445.4 minutes for the pressure sensor technique. Both techniques recorded an average of 13.3 rumination phases with a mean duration of 30.3 (direct observation) and of 30.2 (pressure sensor) minutes. Total time spent ruminating per day, number of cuds per day and chewing cycles per cud were 389.3 and 388.3 minutes, 410.1 and 410.0 and 60.0 and 60.3 for direct observation and pressure sensor technique, respectively. There was a significant difference between the two methods with respect to mean number of chewing cycles per day (24′669, direct observation vs. 24′751, pressure sensor, P < 0.05, paired t-test). There were strong correlations between the two recording methods with correlation coefficients ranging from 0.98 to 1.00. Conclusions The results confirmed that measurements of eating and rumination variables obtained via the pressure sensor technique are in

Novel threshold pressure sensors based on nonlinear dynamics of MEMS resonators

NASA Astrophysics Data System (ADS)

Hasan, Mohammad H.; Alsaleem, Fadi M.; Ouakad, Hassen M.

2018-06-01

Triggering an alarm in a car for low air-pressure in the tire or tripping an HVAC compressor if the refrigerant pressure is lower than a threshold value are examples for applications where measuring the amount of pressure is not as important as determining if the pressure has exceeded a threshold value for an action to occur. Unfortunately, current technology still relies on analog pressure sensors to perform this functionality by adding a complex interface (extra circuitry, controllers, and/or decision units). In this paper, we demonstrate two new smart tunable-threshold pressure switch concepts that can reduce the complexity of a threshold pressure sensor. The first concept is based on the nonlinear subharmonic resonance of a straight double cantilever microbeam with a proof mass and the other concept is based on the snap-through bi-stability of a clamped-clamped MEMS shallow arch. In both designs, the sensor operation concept is simple. Any actuation performed at a certain pressure lower than a threshold value will activate a nonlinear dynamic behavior (subharmonic resonance or snap-through bi-stability) yielding a large output that would be interpreted as a logic value of ONE, or ON. Once the pressure exceeds the threshold value, the nonlinear response ceases to exist, yielding a small output that would be interpreted as a logic value of ZERO, or OFF. A lumped, single degree of freedom model for the double cantilever beam, that is validated using experimental data, and a continuous beam model for the arch beam, are used to simulate the operation range of the proposed sensors by identifying the relationship between the excitation signal and the critical cut-off pressure.

Wireless contactless pressure measurement of an LC passive pressure sensor with a novel antenna for high-temperature applications

NASA Astrophysics Data System (ADS)

Li, Chen; Tan, Qiu-Lin; Xue, Chen-Yang; Zhang, Wen-Dong; Li, Yun-Zhi; Xiong, Ji-Jun

2015-04-01

In this paper, a novel antenna is proposed for high-temperature testing, which can make the high-temperature pressure characteristics of a wireless passive ceramic pressure sensor demonstrated at up to a temperature of 600 °C. The design parameters of the antenna are similar to those of the sensor, which will increase the coupling strength between the sensor and testing antenna. The antenna is fabricated in thick film integrated technology, and the properties of the alumina ceramic and silver ensure the feasibility of the antenna in high-temperature environments. The sensor, coupled with the ceramic antenna, is investigated using a high-temperature pressure testing platform. The experimental measurement results show that the pressure signal in a harsh environment can be detected by the frequency diversity of the sensor. Project supported by the National Natural Science Foundation for Distinguished Young Scholars, China (Grant No. 51425505), the National Natural Science Foundation of China (Grant No. 61471324), the Program for the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi Province, China (Grant No. 2013-077), and the Graduate Students Outstanding Innovation Project of Shanxi Province, China (Grant No. 20143020).

Fiber-optic photoelastic pressure sensor with fiber-loss compensation

NASA Technical Reports Server (NTRS)

Beheim, G.; Anthan, D. J.

1987-01-01

A new fiber-optic pressure sensor is described that has high immunity to the effects of fiber-loss variations. This device uses the photoelastic effect to modulate the proportion of the light from each of two input fibers that is coupled into each of two output fibers. This four-fiber link permits two detectors to be used to measure the sensor's responses to the light from each of two independently controlled sources. These four detector outputs are processed to yield a loss-compensated signal that is a stable and sensitive pressure indicator.

Balloon-borne pressure sensor performance evaluation utilizing tracking radars

NASA Technical Reports Server (NTRS)

Norcross, G. A.; Brooks, R. L.

1983-01-01

The pressure sensors on balloon-borne sondes relate the sonde measurements to height above the Earth's surface through the hypsometric equation. It is crucial that sondes used to explore the vertical structure of the atmosphere do not contribute significant height errors to their measurements of atmospheric constituent concentrations and properties. A series of radiosonde flights was conducted. In most cases, each flight consisted of two sondes attached to a single balloon and each flight was tracked by a highly accurate C-band radar. For the first 19 radiosonde flights, the standard aneroid cell baroswitch assembly used was the pressure sensor. The last 26 radiosondes were equipped with a premium grade aneroid cell baroswitch assembly sensor and with a hypsometer. It is shown that both aneroid cell baroswitch sensors become increasingly inaccurate with altitude. The hypsometer radar differences are not strongly dependent upon altitude and it is found that the standard deviation of the differences at 35 km is 0.179 km.

[Pressure sensors to prevent cardiac decompensation].

PubMed

Klug, Didier

2017-11-01

Most cases of hospitalisation for heart failure are preceded by episodes of cardiac decompensation. Preventing these episodes would improve quality of life and reduce mortality and treatment costs. The monitoring of intracardiac pressures, using innovative sensors, coupled with telemedicine, offers interesting perspectives. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

A GENERIC PACKAGING TECHNIQUE USING FLUIDIC ISOLATION FOR LOW-DRIFT IMPLANTABLE PRESSURE SENSORS.

PubMed

Kim, A; Powell, C R; Ziaie, B

2015-06-01

This paper reports on a generic packaging method for reducing drift in implantable pressure sensors. The described technique uses fluidic isolation by encasing the pressure sensor in a liquid-filled medical-grade polyurethane balloon; thus, isolating it from surrounding aqueous environment that is the major source of baseline drift. In-vitro tests using commercial micromachined piezoresistive pressure sensors show an average baseline drift of 0.006 cmH 2 O/day (0.13 mmHg/month) for over 100 days of saline soak test, as compared to 0.101 cmH 2 O/day (2.23 mmHg/month) for a non-fluidic-isolated one soaked for 18 days. To our knowledge, this is the lowest reported drift for an implantable pressure sensor.

Evaluation of Flexible Force Sensors for Pressure Monitoring in Treatment of Chronic Venous Disorders.

PubMed

Parmar, Suresh; Khodasevych, Iryna; Troynikov, Olga

2017-08-21

The recent use of graduated compression therapy for treatment of chronic venous disorders such as leg ulcers and oedema has led to considerable research interest in flexible and low-cost force sensors. Properly applied low pressure during compression therapy can substantially improve the treatment of chronic venous disorders. However, achievement of the recommended low pressure levels and its accurate determination in real-life conditions is still a challenge. Several thin and flexible force sensors, which can also function as pressure sensors, are commercially available, but their real-life sensing performance has not been evaluated. Moreover, no researchers have reported information on sensor performance during static and dynamic loading within the realistic test conditions required for compression therapy. This research investigated the sensing performance of five low-cost commercial pressure sensors on a human-leg-like test apparatus and presents quantitative results on the accuracy and drift behaviour of these sensors in both static and dynamic conditions required for compression therapy. Extensive experimental work on this new human-leg-like test setup demonstrated its utility for evaluating the sensors. Results showed variation in static and dynamic sensing performance, including accuracy and drift characteristics. Only one commercially available pressure sensor was found to reliably deliver accuracy of 95% and above for all three test pressure points of 30, 50 and 70 mmHg.

Evaluation of Flexible Force Sensors for Pressure Monitoring in Treatment of Chronic Venous Disorders

PubMed Central

Parmar, Suresh; Khodasevych, Iryna; Troynikov, Olga

2017-01-01

The recent use of graduated compression therapy for treatment of chronic venous disorders such as leg ulcers and oedema has led to considerable research interest in flexible and low-cost force sensors. Properly applied low pressure during compression therapy can substantially improve the treatment of chronic venous disorders. However, achievement of the recommended low pressure levels and its accurate determination in real-life conditions is still a challenge. Several thin and flexible force sensors, which can also function as pressure sensors, are commercially available, but their real-life sensing performance has not been evaluated. Moreover, no researchers have reported information on sensor performance during static and dynamic loading within the realistic test conditions required for compression therapy. This research investigated the sensing performance of five low-cost commercial pressure sensors on a human-leg-like test apparatus and presents quantitative results on the accuracy and drift behaviour of these sensors in both static and dynamic conditions required for compression therapy. Extensive experimental work on this new human-leg-like test setup demonstrated its utility for evaluating the sensors. Results showed variation in static and dynamic sensing performance, including accuracy and drift characteristics. Only one commercially available pressure sensor was found to reliably deliver accuracy of 95% and above for all three test pressure points of 30, 50 and 70 mmHg. PMID:28825672

Left Atrial Pressure Monitoring With an Implantable Wireless Pressure Sensor After Implantation of a Left Ventricular Assist Device

PubMed Central

Baranowski, Jacek; Delshad, Baz; Ahn, Henrik

2017-01-01

After implantation of a continuous-flow left ventricular assist device (LVAD), left atrial pressure (LAP) monitoring allows for the precise management of intravascular volume, inotropic therapy, and pump speed. In this case series of 4 LVAD recipients, we report the first clinical use of this wireless pressure sensor for the long-term monitoring of LAP during LVAD support. A wireless microelectromechanical system pressure sensor (Titan, ISS Inc., Ypsilanti, MI) was placed in the left atrium in four patients at the time of LVAD implantation. Titan sensor LAP was measured in all four patients on the intensive care unit and in three patients at home. Ramped speed tests were performed using LAP and echocardiography in three patients. The left ventricular end-diastolic diameter (cm), flow (L/min), power consumption (W), and blood pressure (mm Hg) were measured at each step. Measurements were performed over 36, 84, 137, and 180 days, respectively. The three discharged patients had equipment at home and were able to perform daily recordings. There were significant correlations between sensor pressure and pump speed, LV and LA size and pulmonary capillary wedge pressure, respectively (r = 0.92–0.99, p < 0.05). There was no device failure, and there were no adverse consequences of its use. PMID:27676410

Thin and Flexible Carbon Nanotube-Based Pressure Sensors with Ultra-wide Sensing Range.

PubMed

Doshi, Sagar M; Thostenson, Erik T

2018-06-26

A scalable electrophoretic deposition (EPD) approach is used to create novel thin, flexible and lightweight carbon nanotube-based textile pressure sensors. The pressure sensors can be produced using an extensive variety of natural and synthetic fibers. These piezoresistive sensors are sensitive to pressures ranging from the tactile range (< 10 kPa), in the body weight range (~ 500 kPa), and very high pressures (~40 MPa). The EPD technique enables the creation of a uniform carbon nanotube-based nanocomposite coating, in the range of 250-750 nm thick, of polyethyleneimine (PEI) functionalized carbon nanotubes on non-conductive fibers. In this work, non-woven aramid fibers are coated by EPD onto a backing electrode followed by film formation onto the fibers creating a conductive network. The electrically conductive nanocomposite coating is firmly bonded to the fiber surface and shows piezoresistive electrical/mechanical coupling. The pressure sensor displays a large in-plane change in electrical conductivity with applied out-of-plane pressure. In-plane conductivity change results from fiber/fiber contact as well as the formation of a sponge-like piezoresistive nanocomposite "interphase" between the fibers. The resilience of the nanocomposite interphase enables sensing of high pressures without permanent changes to the sensor response, showing high repeatability.

Pressure sensitivity analysis of fiber Bragg grating sensors

NASA Astrophysics Data System (ADS)

Mrad, Nezih; Sridharan, Vasant; Kazemi, Alex

2014-09-01

Recent development in fiber optic sensing technology has mainly focused on discrete sensing, particularly, sensing systems with potential multiplexing and multi-parameter capabilities. Bragg grating fiber optic sensors have emerged as the non-disputed champion for multiplexing and simultaneous multi-parameter sensing for emerging high value structural components, advanced processing and manufacturing capabilities and increased critical infrastructure resilience applications. Although the number of potential applications for this sensing technology is large and spans the domains of medicine, manufacturing, aerospace, and public safety; critical issues such as fatigue life, sensitivity, accuracy, embeddability, material/sensor interface integrity, and universal demodulation systems still need to be addressed. The purpose of this paper is to primarily evaluate Commercial-Of-The-Shelf (COTS) Fiber Bragg Grating (FBG) sensors' sensitivity to pressure, often neglected in several applications. The COTS fiber sensitivity to pressure is further evaluated for two types of coatings (Polyimide and Acrylate), and different arrangements (arrayed and single).

MEMS fiber-optic Fabry-Perot pressure sensor for high temperature application

NASA Astrophysics Data System (ADS)

Fang, G. C.; Jia, P. G.; Cao, Q.; Xiong, J. J.

2016-10-01

We design and demonstrate a fiber-optic Fabry-Perot pressure sensor (FOFPPS) for high-temperature sensing by employing micro-electro-mechanical system (MEMS) technology. The FOFPPS is fabricated by anodically bonding the silicon wafer and the Pyrex glass together and fixing the facet of the optical fiber in parallel with the silicon surface by glass frit and organic adhesive. The silicon wafer can be reduced through dry etching technology to construct the sensitive diaphragm. The length of the cavity changes with the deformation of the diaphragm due to the loaded pressure, which leads to a wavelength shift of the interference spectrum. The pressure can be gauged by measuring the wavelength shift. The pressure experimental results show that the sensor has linear pressure sensitivities ranging from 0 kPa to 600 kPa at temperature range between 20°C to 300°C. The pressure sensitivity at 300°C is approximately 27.63 pm/kPa. The pressure sensitivities gradually decrease with increasing the temperature. The sensor also has a linear thermal drift when temperature changes from 20°C - 300°C.

Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber.

PubMed

Liu, Zhengyong; Htein, Lin; Lee, Kang-Kuen; Lau, Kin-Tak; Tam, Hwa-Yaw

2018-01-08

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10 -4 , 1.23 × 10 -4 , respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

Pressure standards and sensors up to 3 GPa, actual state and development trends

NASA Astrophysics Data System (ADS)

Wisniewski, Roland; Molinar, Gianfranco

1999-04-01

Metrological problems connected with pressure standards and sensors up to 3 GPa as an introduction to the pressure measurements in the so-called “GIGAPASCAL REGION”, 1-100 GPa, are discussed. Re-examination of Bi I-Bi II phase transition pressure as a fixed point of the International Practical Pressure Scale and correction of the NaCl Pressure Scale is proposed. Well-established sensors as candidates for secondary pressure standards up to 3 GPa are briefly presented.

PEDOT:PSS/QCM-based multimodal humidity and pressure sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muckley, Eric S.; Lynch, James; Kumar, Rajeev

A room-temperature multimodal sensor composed of PEDOT:PSS deposited on an AT-cut quartz crystalmicrobalance (QCM) crystal has been fabricated. The nonlinear resistive and frequency sensor responses aredeconvolved using an articial neural network (ANN), which allows the single sensor to function simultane-ously as a relative humidity (RH) sensor and a pressure sensor using only two electrodes. We demonstratethat the predictive ability of the sensor is highly inuenced by the data used to train the ANN. When trainingsets are tailored to resemble the operating conditions of the sensor, the sensor achieves an average resolutionof < 3% RH from 0-100% RH, even after Hmore » 2O saturation occurs on the surface. Our results indicate thatANNs show strong promise for improving the resolution of low cost gas sensors and for expanding the rangeof environmental conditions in which a given sensor can operate.« less

PEDOT:PSS/QCM-based multimodal humidity and pressure sensor

DOE PAGES

Muckley, Eric S.; Lynch, James; Kumar, Rajeev; ...

2016-05-11

A room-temperature multimodal sensor composed of PEDOT:PSS deposited on an AT-cut quartz crystalmicrobalance (QCM) crystal has been fabricated. The nonlinear resistive and frequency sensor responses aredeconvolved using an articial neural network (ANN), which allows the single sensor to function simultane-ously as a relative humidity (RH) sensor and a pressure sensor using only two electrodes. We demonstratethat the predictive ability of the sensor is highly inuenced by the data used to train the ANN. When trainingsets are tailored to resemble the operating conditions of the sensor, the sensor achieves an average resolutionof < 3% RH from 0-100% RH, even after Hmore » 2O saturation occurs on the surface. Our results indicate thatANNs show strong promise for improving the resolution of low cost gas sensors and for expanding the rangeof environmental conditions in which a given sensor can operate.« less

Research of pressure sensor based on the fiber Bragg grating for permanent downwell monitoring application

NASA Astrophysics Data System (ADS)

Liu, Lina; Long, Pin; Liu, Tiegen

2004-11-01

Timely, accurate and reliable pressure information about how the reservoir is performing is an important component to optimizing oil yield and production rates. This paper reviews the use of fiber optical pressure sensor for downhole monitoring in the oil industry. Several types of pressure transducer with different characteristics have been introduced. Due to their multiplexing capabilities and versatility ,the use of Bragg grating sensors appears to be particularly suited for this application. A sensor for accurate and long term fluid pressure monitoring based on optical fiber Bragg gratings(FBGs) is developed. The sensor converts fluid pressure into optical fiber strain by means of a mechanical transducer to enhance its sensitivity to pressure. It can also implement distributed or multiplexed sensing. The sensor operation is studied at pressure up to 100 Mpa(1000bar) and the tested temperature to ~175°. It is possible to be used in the well.

A miniature extrinsic fiber Fabry-Perot pressure sensor based on fiber etching

NASA Astrophysics Data System (ADS)

Ge, Yixian; Zhou, Junping; Wang, Tingting

2011-11-01

A miniature fiber optic pressure sensor based on Fabry-Perot interference fabricated on the tip of a single mode (SM) fiber is presented. The sensor measures only 125μm in diameter. A Fabry-Perot cavity and a thin silica diaphragm are fabricated by simple techniques involving only cleaving, wet chemical etching and fusion splicing. Interference pattern of the sensor is analyzed and issues in sensor design are discussed. The overall chemical reaction of the fiber wet etching is specifically represented. Pressure testing system is carried out. By tracing a peak point in the interference spectrum, the gap length of the sensor can be demodulated. Experimental results show the sensor has a good linearity. The sensor is made entirely of fused silica, whose structure has good stability, cabinet, simple for fabrication and low cost.

Accelerated Biofluid Filling in Complex Microfluidic Networks by Vacuum-Pressure Accelerated Movement (V-PAM).

PubMed

Yu, Zeta Tak For; Cheung, Mei Ki; Liu, Shirley Xiaosu; Fu, Jianping

2016-09-01

Rapid fluid transport and exchange are critical operations involved in many microfluidic applications. However, conventional mechanisms used for driving fluid transport in microfluidics, such as micropumping and high pressure, can be inaccurate and difficult for implementation for integrated microfluidics containing control components and closed compartments. Here, a technology has been developed termed Vacuum-Pressure Accelerated Movement (V-PAM) capable of significantly enhancing biofluid transport in complex microfluidic environments containing dead-end channels and closed chambers. Operation of the V-PAM entails a pressurized fluid loading into microfluidic channels where gas confined inside can rapidly be dissipated through permeation through a thin, gas-permeable membrane sandwiched between microfluidic channels and a network of vacuum channels. Effects of different structural and operational parameters of the V-PAM for promoting fluid filling in microfluidic environments have been studied systematically. This work further demonstrates the applicability of V-PAM for rapid filling of temperature-sensitive hydrogels and unprocessed whole blood into complex irregular microfluidic networks such as microfluidic leaf venation patterns and blood circulatory systems. Together, the V-PAM technology provides a promising generic microfluidic tool for advanced fluid control and transport in integrated microfluidics for different microfluidic diagnosis, organs-on-chips, and biomimetic studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stretchable Array of Highly Sensitive Pressure Sensors Consisting of Polyaniline Nanofibers and Au-Coated Polydimethylsiloxane Micropillars.

PubMed

Park, Heun; Jeong, Yu Ra; Yun, Junyeong; Hong, Soo Yeong; Jin, Sangwoo; Lee, Seung-Jung; Zi, Goangseup; Ha, Jeong Sook

2015-10-27

We report on the facile fabrication of a stretchable array of highly sensitive pressure sensors. The proposed pressure sensor consists of the top layer of Au-deposited polydimethylsiloxane (PDMS) micropillars and the bottom layer of conductive polyaniline nanofibers on a polyethylene terephthalate substrate. The sensors are operated by the changes in contact resistance between Au-coated micropillars and polyaniline according to the varying pressure. The fabricated pressure sensor exhibits a sensitivity of 2.0 kPa(-1) in the pressure range below 0.22 kPa, a low detection limit of 15 Pa, a fast response time of 50 ms, and high stability over 10000 cycles of pressure loading/unloading with a low operating voltage of 1.0 V. The sensor is also capable of noninvasively detecting human-pulse waveforms from carotid and radial artery. A 5 × 5 array of the pressure sensors on the deformable substrate, which consists of PDMS islands for sensors and the mixed thin film of PDMS and Ecoflex with embedded liquid metal interconnections, shows stable sensing of pressure under biaxial stretching by 15%. The strain distribution obtained by the finite element method confirms that the maximum strain applied to the pressure sensor in the strain-suppressed region is less than 0.04% under a 15% biaxial strain of the unit module. This work demonstrates the potential application of our proposed stretchable pressure sensor array for wearable and artificial electronic skin devices.

Improved Thermal-Vacuum Compatible Flat Plate Radiometric Souce for System-Level Testing of Optical Sensors

NASA Technical Reports Server (NTRS)

Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.

2015-01-01

This work describes the development of an improved vacuum compatible flat plate radiometric source used for characterizing and calibrating remote optical sensors, in situ, throughout their testing period. The original flat plate radiometric source was developed for use by the VIIRS instrument during the NPOESS Preparatory Project (NPP). Following this effort, the FPI has had significant upgrades in order to improve both the radiometric throughput and uniformity. Results of the VIIRS testing with the reconfigured FPI are reported and discussed.

A novel hydrogel based piezoresistive pressure sensor platform for chemical sensing

NASA Astrophysics Data System (ADS)

Orthner, Michael P.

New hydrogel-based micropressure sensor arrays for use in the fields of chemical sensing, physiological monitoring, and medical diagnostics are developed and demonstrated. This sensor technology provides reliable, linear, and accurate measurements of hydrogel swelling pressures, a function of ambient chemical concentrations. For the first time, perforations were implemented into the pressure sensors piezoresistive diaphragms, used to simultaneously increase sensor sensitivity and permit diffusion of analytes into the hydrogel cavity. It was shown through analytical and numerical (finite element) methods that pore shape, location, and size can be used to modify the diaphragm mechanics and concentrate stress within the piezoresistors, thus improving electrical output (sensitivity). An optimized pore pattern was chosen based on these numerical calculations. Fabrication was performed using a 14-step semiconductor fabrication process implementing a combination of potassium hydroxide (KOH) and deep reactive ion etching (DRIE) to create perforations. The sensor arrays (2x2) measure approximately 3 x 5 mm2 and used to measure full scale pressures of 50, 25, and 5 kPa, respectively. These specifications were defined by the various swelling pressures of ionic strength, pH and glucose specific hydrogels that were targeted in this work. Initial characterization of the sensor arrays was performed using a custom built bulge testing apparatus that simultaneously measured deflection (optical profilometry), pressure, and electrical output. The new perforated diaphragm sensors were found to be fully functional with sensitivities ranging from 23 to 252 muV/V-kPa with full scale output (FSO) ranging from 5 to 80 mV. To demonstrate proof of concept, hydrogels sensitive to changes in ionic strength were synthesized using hydroxypropyl-methacrylate (HPMA), N,N-dimethylaminoethyl-methacrylate (DMA) and a tetra-ethyleneglycol-dimethacrylate (TEGDMA) crosslinker. This hydrogel quickly and

PBO Borehole Strainmeters and Pore Pressure Sensors: Recording Hydrological Strain Signals

NASA Astrophysics Data System (ADS)

Gottlieb, M. H.; Hodgkinson, K. M.; Mencin, D.; Henderson, D. B.; Johnson, W.; Van Boskirk, E.; Pyatt, C.; Mattioli, G. S.

2017-12-01

UNAVCO operates a network of 75 borehole strainmeters along the west coast of the United States and Vancouver Island, Canada as part of the Plate Boundary Observatory (PBO), the geodetic component of the NSF-funded Earthscope program. Borehole strainmeters are designed to detect variations in the strain field at the nanostrain level and can easily detect transient strains caused by aseismic creep events, Episodic Tremor and Slip (ETS) events and seismically induced co- and post-seimic signals. In 2016, one strainmeter was installed in an Oklahoma oil field to characterize in-situ deformation during CO2 injection. Twenty-three strainmeter sites also have pore pressure sensors to measure fluctuations in groundwater pressure. Both the strainmeter network and the pore pressure sensors provide unique data against which those using water-level measurements, GPS time-series or InSAR data can compare possible subsidence signals caused by groundwater withdrawal or fluid re-injection. Operating for 12 years, the PBO strainmeter and pore pressure network provides a long-term, continuous, 1-sps record of deformation. PBO deploys GTSM21 tensor strainmeters from GTSM Technologies, which consist of four horizontal strain gauges stacked vertically, at different orientations, within a single 2 m-long instrument. The strainmeters are typically installed at depths of 200 to 250 m and grouted into the bottom of 15 cm diameter boreholes. The pore pressure sensors are Digiquartz Depth Sensors from Paros Scientific. These sensors are installed in 2" PVC, sampling groundwater through a screened section 15 m above the co-located strainmeter. These sensors are also recording at 1-sps with a resolution in the hundredths of hPa. High-rate local barometric pressure data and low-rate rainfall data also available at all locations. PBO Strainmeter and pore pressure data are available in SEED, SAC-ASCII and time-stamped ASCII format from the IRIS Data Managements Center. Strainmeter data are

Multiscale Hierarchical Design of a Flexible Piezoresistive Pressure Sensor with High Sensitivity and Wide Linearity Range.

PubMed

Shi, Jidong; Wang, Liu; Dai, Zhaohe; Zhao, Lingyu; Du, Mingde; Li, Hongbian; Fang, Ying

2018-05-30

Flexible piezoresistive pressure sensors have been attracting wide attention for applications in health monitoring and human-machine interfaces because of their simple device structure and easy-readout signals. For practical applications, flexible pressure sensors with both high sensitivity and wide linearity range are highly desirable. Herein, a simple and low-cost method for the fabrication of a flexible piezoresistive pressure sensor with a hierarchical structure over large areas is presented. The piezoresistive pressure sensor consists of arrays of microscale papillae with nanoscale roughness produced by replicating the lotus leaf's surface and spray-coating of graphene ink. Finite element analysis (FEA) shows that the hierarchical structure governs the deformation behavior and pressure distribution at the contact interface, leading to a quick and steady increase in contact area with loads. As a result, the piezoresistive pressure sensor demonstrates a high sensitivity of 1.2 kPa -1 and a wide linearity range from 0 to 25 kPa. The flexible pressure sensor is applied for sensitive monitoring of small vibrations, including wrist pulse and acoustic waves. Moreover, a piezoresistive pressure sensor array is fabricated for mapping the spatial distribution of pressure. These results highlight the potential applications of the flexible piezoresistive pressure sensor for health monitoring and electronic skin. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Embedding of MEMS pressure and temperature sensors in carbon fiber composites: a manufacturing approach

NASA Astrophysics Data System (ADS)

Javidinejad, Amir; Joshi, Shiv P.

2000-06-01

In this paper embedding of surface mount pressure and temperature sensors in the Carbon fiber composites are described. A commercially available surface mount pressure and temperature sensor are used for embedding in a composite lay- up of IM6/HST-7, IM6/3501 and AS4/E7T1-2 prepregs. The fabrication techniques developed here are the focus of this paper and provide for a successful embedding procedure of pressure sensors in fibrous composites. The techniques for positioning and insulating, the sensor and the lead wires, from the conductive carbon prepregs are described and illustrated. Procedural techniques are developed and discussed for isolating the sensor's flow-opening, from the exposure to the prepreg epoxy flow and exposure to the fibrous particles, during the autoclave curing of the composite laminate. The effects of the autoclave cycle (if any) on the operation of the embedded pressure sensor are discussed.

A Wireless Embedded Sensor based on Magnetic Higher-order Harmonic Fields: Application to Liquid Pressure Monitoring

PubMed Central

Tan, Ee Lim; Pereles, Brandon D.

2010-01-01

A wireless sensor based on the magnetoelastic, magnetically soft ferromagnetic alloy was constructed for remote measurement of pressure in flowing fluids. The pressure sensor was a rectangular strip of ferromagnetic alloy Fe40Ni38Mo4B18 adhered on a solid polycarbonate substrate and protected by a thin polycarbonate film. Upon excitation of a time-varying magnetic field through an excitation coil, the magnetically soft sensor magnetized and produced higher-order harmonic fields, which were detected through a detection coil. Under varying pressures, the sensor's magnetoelastic property caused a change in its magnetization, altering the amplitudes of the higher-order harmonic fields. A theoretical model was developed to describe the effect of pressure on the sensor's higher order harmonic fields. Experimental observations showed the 2nd order harmonic field generated by the pressure sensor was correlated to the surrounding fluid pressure, consistent with the theoretical results. Furthermore, it was demonstrated that the sensor exhibited good repeatability and stability with minimal drift. Sensors with smaller dimensions were shown to have greater sensitivity but lower pressure range as compared to their larger counterparts. Since the sensor signal was also dependent on the location of the sensor with respect to the excitation/detection coil, a calibration algorithm was developed to eliminate signal variations due to the changing sensor location. Because of its wireless and passive nature, this sensor is useful for continuous and long-term monitoring of pressure at inaccessible areas. For example, sensors with these capabilities are suitable to be used in biomedical applications where permanent implantation and long-term monitoring are needed. PMID:20514363

A hybrid demodulation method of fiber-optic Fabry-Perot pressure sensor

NASA Astrophysics Data System (ADS)

Yu, Le; Lang, Jianjun; Pan, Yong; Wu, Di; Zhang, Min

2013-12-01

The fiber-optic Fabry-Perot pressure sensors have been widely applied to measure pressure in oilfield. For multi-well it will take a long time (dozens of seconds) to demodulate downhole pressure values of all wells by using only one demodulation system and it will cost a lot when every well is equipped with one system, which heavily limits the sensor applied in oilfield. In present paper, a new hybrid demodulation method, combining the windowed nonequispaced discrete Fourier Transform (nDFT) method with segment search minimum mean square error estimation (MMSE) method, was developed, by which the demodulation time can be reduced to 200ms, i.e., measuring 10 channels/wells was less than 2s. Besides, experimental results showed the demodulation cavity length of the fiber-optic Fabry-Perot sensor has a maximum error of 0.5 nm and consequently pressure measurement accuracy can reach 0.4% F.S.

Temperature and pressure fiber-optic sensors applied to minimally invasive diagnostics and therapies

NASA Astrophysics Data System (ADS)

Hamel, Caroline; Pinet, Éric

2006-02-01

We present how fiber-optic temperature or pressure sensors could be applied to minimally invasive diagnostics and therapies. For instance a miniature pressure sensor based on micro-optical mechanical systems (MOMS) could solve most of the problems associated with fluidic pressure transduction presently used for triggering purposes. These include intra-aortic balloon pumping (IABP) therapy and other applications requiring detection of fast and/or subtle fluid pressure variations such as for intracranial pressure monitoring or for urology diagnostics. As well, miniature temperature sensors permit minimally invasive direct temperature measurement in diagnostics or therapies requiring energy transfer to living tissues. The extremely small size of fiber-optic sensors that we have developed allows quick and precise in situ measurements exactly where the physical parameters need to be known. Furthermore, their intrinsic immunity to electromagnetic interference (EMI) allows for the safe use of EMI-generating therapeutic or diagnostic equipments without compromising the signal quality. With the trend of ambulatory health care and the increasing EMI noise found in modern hospitals, the use of multi-parameter fiber-optic sensors will improve constant patient monitoring without any concern about the effects of EMI disturbances. The advantages of miniature fiberoptic sensors will offer clinicians new monitoring tools that open the way for improved diagnostic accuracy and new therapeutic technologies.

An ionization gauge for ultrahigh vacuum measurement based on a carbon nanotube cathode

NASA Astrophysics Data System (ADS)

Zhang, Huzhong; Cheng, Yongjun; Sun, Jian; Wang, Yongjun; Xi, Zhenhua; Dong, Meng; Li, Detian

2017-10-01

This work reports on the complete design and the properties of an ionization gauge based on a carbon nanotube cathode, which can measure ultrahigh vacuum without thermal effects. The gauge is composed of a pressure sensor and an electronic controller. This pressure sensor is constructed based on a hot-cathode ionization gauge, where the traditional hot filament is replaced by an electron source prepared with multi-wall nanotubes. Besides, an electronic controller was developed for bias voltage supply, low current detection, and pressure indication. The gauge was calibrated in the pressure range of 10-8 to 10-4 Pa in a XHV/UHV calibration apparatus. The gauge shows good linear characteristics in different gases. The calibrated sensitivity is 0.035 Pa-1 in N2, and the standard deviation of the sensitivity is about 1.1%. In addition, the stability of the sensitivity was learned in a long period. The standard deviation of the sensitivity factor "S" during one year is 2.0% for Ar and 1.6% for N2.

Soft-Matter Resistive Sensor for Measuring Shear and Pressure Stresses

NASA Astrophysics Data System (ADS)

Tepayotl-Ramirez, Daniel; Roberts, Peter; Majidi, Carmel

2013-03-01

Building on emerging paradigms in soft-matter electronics, we introduce liquid-phase electronic sensors that simultaneously measures elastic pressure and shear deformation. The sensors are com- posed of a sheet of elastomer that is embedded with fluidic channels containing eutectic Gallium- Indium (EGaIn), a metal alloy that is liquid at room temperature. Applying pressure or shear traction to the surface of the surrounding elastomer causes the elastomer to elastically deform and changes the geometry and electrical properties of the embedded liquid-phase circuit elements. We introduce analytic models that predict the electrical response of the sensor to prescribed surface tractions. These models are validated with both Finite Element Analysis (FEA) and experimental measurements.

Cold cathode vacuum gauging system

DOEpatents

Denny, Edward C.

2004-03-09

A vacuum gauging system of the cold cathode type is provided for measuring the pressure of a plurality of separate vacuum systems, such as in a gas centrifuge cascade. Each casing is fitted with a gauge tube assembly which communicates with the vacuum system in the centrifuge casing. Each gauge tube contains an anode which may be in the form of a slender rod or wire hoop and a cathode which may be formed by the wall of the gauge tube. The tube is provided with an insulated high voltage connector to the anode which has a terminal for external connection outside the vacuum casing. The tube extends from the casing so that a portable magnet assembly may be inserted about the tube to provide a magnetic field in the area between the anode and cathode necessary for pressure measurements in a cold cathode-type vacuum gauge arrangement. The portable magnetic assembly is provided with a connector which engages the external high voltage terminal for providing power to the anode within in the gauge tube. Measurement is made in the same manner as the prior cold cathode gauges in that the current through the anode to the cathode is measured as an indication of the pressure. By providing the portable magnetic assembly, a considerable savings in cost, installation, and maintenance of vacuum gauges for pressure measurement in a gas centrifuge cascade is realizable.

Flexible hemispheric microarrays of highly pressure-sensitive sensors based on breath figure method.

PubMed

Wang, Zhihui; Zhang, Ling; Liu, Jin; Jiang, Hao; Li, Chunzhong

2018-05-30

Recently, flexible pressure sensors featuring high sensitivity, broad sensing range and real-time detection have aroused great attention owing to their crucial role in the development of artificial intelligent devices and healthcare systems. Herein, highly sensitive pressure sensors based on hemisphere-microarray flexible substrates are fabricated via inversely templating honeycomb structures deriving from a facile and static breath figure process. The interlocked and subtle microstructures greatly improve the sensing characteristics and compressibility of the as-prepared pressure sensor, endowing it a sensitivity as high as 196 kPa-1 and a wide pressure sensing range (0-100 kPa), as well as other superior performance, including a lower detection limit of 0.5 Pa, fast response time (<26 ms) and high reversibility (>10 000 cycles). Based on the outstanding sensing performance, the potential capability of our pressure sensor in capturing physiological information and recognizing speech signals has been demonstrated, indicating promising application in wearable and intelligent electronics.

Highly Sensitive, Transparent, and Durable Pressure Sensors Based on Sea-Urchin Shaped Metal Nanoparticles.

PubMed

Lee, Donghwa; Lee, Hyungjin; Jeong, Youngjun; Ahn, Yumi; Nam, Geonik; Lee, Youngu

2016-11-01

Highly sensitive, transparent, and durable pressure sensors are fabricated using sea-urchin-shaped metal nanoparticles and insulating polyurethane elastomer. The pressure sensors exhibit outstanding sensitivity (2.46 kPa -1 ), superior optical transmittance (84.8% at 550 nm), fast response/relaxation time (30 ms), and excellent operational durability. In addition, the pressure sensors successfully detect minute movements of human muscles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pressure mapping with textile sensors for compression therapy monitoring.

PubMed

Baldoli, Ilaria; Mazzocchi, Tommaso; Paoletti, Clara; Ricotti, Leonardo; Salvo, Pietro; Dini, Valentina; Laschi, Cecilia; Francesco, Fabio Di; Menciassi, Arianna

2016-08-01

Compression therapy is the cornerstone of treatment in the case of venous leg ulcers. The therapy outcome is strictly dependent on the pressure distribution produced by bandages along the lower limb length. To date, pressure monitoring has been carried out using sensors that present considerable drawbacks, such as single point instead of distributed sensing, no shape conformability, bulkiness and constraints on patient's movements. In this work, matrix textile sensing technologies were explored in terms of their ability to measure the sub-bandage pressure with a suitable temporal and spatial resolution. A multilayered textile matrix based on a piezoresistive sensing principle was developed, calibrated and tested with human subjects, with the aim of assessing real-time distributed pressure sensing at the skin/bandage interface. Experimental tests were carried out on three healthy volunteers, using two different bandage types, from among those most commonly used. Such tests allowed the trends of pressure distribution to be evaluated over time, both at rest and during daily life activities. Results revealed that the proposed device enables the dynamic assessment of compression mapping, with a suitable spatial and temporal resolution (20 mm and 10 Hz, respectively). In addition, the sensor is flexible and conformable, thus well accepted by the patient. Overall, this study demonstrates the adequacy of the proposed piezoresistive textile sensor for the real-time monitoring of bandage-based therapeutic treatments. © IMechE 2016.

Vacuum-sealed microcavity formed from suspended graphene by using a low-pressure dry-transfer technique

NASA Astrophysics Data System (ADS)

Takahashi, K.; Ishida, H.; Sawada, K.

2018-01-01

We report the development of a microcavity drum sealed by suspended graphene. The drum is fabricated by using a low-pressure dry-transfer technique, which involves vacuum de-aeration between a graphene sheet and a substrate and raising the temperature to above the glass transition of the supporting poly(methyl methacrylate) film, which serves to increase the real contact area. The result is a suspended graphene sheet with a maximum diameter of 48.6 μm. The Raman spectrum of the suspended graphene has a 2D/G ratio of 1.79 and a few D peaks, which suggests that the material is high-quality single-layer graphene. The dry-transfer technique yields a vacuum-sealed microcavity drum 1.1 μm deep up to 4.5 μm in diameter. The Raman shift indicates that the suspended graphene is subjected to a tensile strain of 0.05%, which is attributed to the pressure difference between the evacuated cavity and the exterior gas.

Battery-free, wireless sensors for full-body pressure and temperature mapping

PubMed Central

Han, Seungyong; Kim, Jeonghyun; Won, Sang Min; Ma, Yinji; Kang, Daeshik; Xie, Zhaoqian; Lee, Kyu-Tae; Chung, Ha Uk; Banks, Anthony; Min, Seunghwan; Heo, Seung Yun; Davies, Charles R.; Lee, Jung Woo; Lee, Chi-Hwan; Kim, Bong Hoon; Li, Kan; Zhou, Yadong; Wei, Chen; Feng, Xue; Huang, Yonggang; Rogers, John A.

2018-01-01

Thin, soft, skin-like sensors capable of precise, continuous measurements of physiological health have broad potential relevance to clinical health care. Use of sensors distributed over a wide area for full-body, spatiotemporal mapping of physiological processes would be a considerable advance for this field. We introduce materials, device designs, wireless power delivery and communication strategies, and overall system architectures for skin-like, battery-free sensors of temperature and pressure that can be used across the entire body. Combined experimental and theoretical investigations of the sensor operation and the modes for wireless addressing define the key features of these systems. Studies with human subjects in clinical sleep laboratories and in adjustable hospital beds demonstrate functionality of the sensors, with potential implications for monitoring of circadian cycles and mitigating risks for pressure-induced skin ulcers. PMID:29618561

Highly stable liquid metal-based pressure sensor integrated with a microfluidic channel.

PubMed

Jung, Taekeon; Yang, Sung

2015-05-21

Pressure measurement is considered one of the key parameters in microfluidic systems. It has been widely used in various fields, such as in biology and biomedical fields. The electrical measurement method is the most widely investigated; however, it is unsuitable for microfluidic systems because of a complicated fabrication process and difficult integration. Moreover, it is generally damaged by large deflection. This paper proposes a thin-film-based pressure sensor that is free from these limitations, using a liquid metal called galinstan. The proposed pressure sensor is easily integrated into a microfluidic system using soft lithography because galinstan exists in a liquid phase at room temperature. We investigated the characteristics of the proposed pressure sensor by calibrating for a pressure range from 0 to 230 kPa (R2 > 0.98) using deionized water. Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30-1000 s(-1). The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively. The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability.

Highly Stable Liquid Metal-Based Pressure Sensor Integrated with a Microfluidic Channel

PubMed Central

Jung, Taekeon; Yang, Sung

2015-01-01

Pressure measurement is considered one of the key parameters in microfluidic systems. It has been widely used in various fields, such as in biology and biomedical fields. The electrical measurement method is the most widely investigated; however, it is unsuitable for microfluidic systems because of a complicated fabrication process and difficult integration. Moreover, it is generally damaged by large deflection. This paper proposes a thin-film-based pressure sensor that is free from these limitations, using a liquid metal called galinstan. The proposed pressure sensor is easily integrated into a microfluidic system using soft lithography because galinstan exists in a liquid phase at room temperature. We investigated the characteristics of the proposed pressure sensor by calibrating for a pressure range from 0 to 230 kPa (R2 > 0.98) using deionized water. Furthermore, the viscosity of various fluid samples was measured for a shear-rate range of 30–1000 s−1. The results of Newtonian and non-Newtonian fluids were evaluated using a commercial viscometer and normalized difference was found to be less than 5.1% and 7.0%, respectively. The galinstan-based pressure sensor can be used in various microfluidic systems for long-term monitoring with high linearity, repeatability, and long-term stability. PMID:26007732

Facile Fabrication of Multi-hierarchical Porous Polyaniline Composite as Pressure Sensor and Gas Sensor with Adjustable Sensitivity

NASA Astrophysics Data System (ADS)

He, Xiao-Xiao; Li, Jin-Tao; Jia, Xian-Sheng; Tong, Lu; Wang, Xiao-Xiong; Zhang, Jun; Zheng, Jie; Ning, Xin; Long, Yun-Ze

2017-08-01

A multi-hierarchical porous polyaniline (PANI) composite which could be used in good performance pressure sensor and adjustable sensitivity gas sensor has been fabricated by a facile in situ polymerization. Commercial grade sponge was utilized as a template scaffold to deposit PANI via in situ polymerization. With abundant interconnected pores throughout the whole structure, the sponge provided sufficient surface for the growth of PANI nanobranches. The flexible porous structure helped the composite to show high performance in pressure detection with fast response and favorable recoverability and gas detection with adjustable sensitivity. The sensing mechanism of the PANI/sponge-based flexible sensor has also been discussed. The results indicate that this work provides a feasible approach to fabricate efficient sensors with advantages of low cost, facile preparation, and easy signal collection.

Facile Fabrication of Multi-hierarchical Porous Polyaniline Composite as Pressure Sensor and Gas Sensor with Adjustable Sensitivity.

PubMed

He, Xiao-Xiao; Li, Jin-Tao; Jia, Xian-Sheng; Tong, Lu; Wang, Xiao-Xiong; Zhang, Jun; Zheng, Jie; Ning, Xin; Long, Yun-Ze

2017-12-01

A multi-hierarchical porous polyaniline (PANI) composite which could be used in good performance pressure sensor and adjustable sensitivity gas sensor has been fabricated by a facile in situ polymerization. Commercial grade sponge was utilized as a template scaffold to deposit PANI via in situ polymerization. With abundant interconnected pores throughout the whole structure, the sponge provided sufficient surface for the growth of PANI nanobranches. The flexible porous structure helped the composite to show high performance in pressure detection with fast response and favorable recoverability and gas detection with adjustable sensitivity. The sensing mechanism of the PANI/sponge-based flexible sensor has also been discussed. The results indicate that this work provides a feasible approach to fabricate efficient sensors with advantages of low cost, facile preparation, and easy signal collection.

The trade-off characteristics of acoustic and pressure sensors for the NASP

NASA Technical Reports Server (NTRS)

Winkler, Martin; Bush, Chuck

1992-01-01

Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty.