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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Fiber optic pressure sensors in skin-friction measurements

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.

Kidwell, R.↗
NASA NTRS2014

Propagation of Radiosonde Pressure Sensor Errors to Ozonesonde Measurements

Several previous studies highlight pressure (or equivalently, pressure altitude) discrepancies between the radiosonde pressure sensor and that derived from a GPS flown with the radiosonde. The offsets vary during the ascent both in absolute and percent pressure differences. To investigate this problem further, a total of 731 radiosonde-ozonesonde launches from the Southern Hemisphere subtropics to Northern mid-latitudes are considered, with launches between 2005 - 2013 from both longer-term and campaign-based intensive stations. Five series of radiosondes from two manufacturers (International Met Systems: iMet, iMet-P, iMet-S, and Vaisala: RS80-15N and RS92-SGP) are analyzed to determine the magnitude of the pressure offset. Additionally, electrochemical concentration cell (ECC) ozonesondes from three manufacturers (Science Pump Corporation; SPC and ENSCI-Droplet Measurement Technologies; DMT) are analyzed to quantify the effects these offsets have on the calculation of ECC ozone (O3) mixing ratio profiles (O3MR) from the ozonesonde-measured partial pressure. Approximately half of all offsets are 0.6 hPa in the free troposphere, with nearly a third 1.0 hPa at 26 km, where the 1.0 hPa error represents 5 persent of the total atmospheric pressure. Pressure offsets have negligible effects on O3MR below 20 km (96 percent of launches lie within 5 percent O3MR error at 20 km). Ozone mixing ratio errors above 10 hPa (30 km), can approach greater than 10 percent ( 25 percent of launches that reach 30 km exceed this threshold). These errors cause disagreement between the integrated ozonesonde-only column O3 from the GPS and radiosonde pressure profile by an average of +6.5 DU. Comparisons of total column O3 between the GPS and radiosonde pressure profiles yield average differences of +1.1 DU when the O3 is integrated to burst with addition of the McPeters and Labow (2012) above-burst O3 column climatology. Total column differences are reduced to an average of -0.5 DU when the O3 profile is integrated to 10 hPa with subsequent addition of the O3 climatology above 10 hPa. The RS92 radiosondes are superior in performance compared to other radiosondes, with average 26 km errors of -0.12 hPa or +0.61 percent O3MR error. iMet-P radiosondes had average 26 km errors of -1.95 hPa or +8.75 percent O3MR error. Based on our analysis, we suggest that ozonesondes always be coupled with a GPS-enabled radiosonde and that pressure-dependent variables, such as O3MR, be recalculated-reprocessed using the GPS-measured altitude, especially when 26 km pressure offsets exceed 1.0 hPa 5 percent.

pressure measurements↗
NASA NTRS1991

Calculation Of Pneumatic Attenuation In Pressure Sensors

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.

Whitmore, Stephen A.↗
NASA NTRS2021

Gravity Wave Observations by the Mars Science Laboratory REMS Pressure Sensor and Comparison with Mesoscale Atmospheric Modeling with MarsWRF

Surface pressure measurements on Mars have revealed a wide variety of atmospheric phenomena. The Mars Science Laboratory Rover Environmental Monitoring Station pressure sensor dataset is now the longest duration record of surface pressure on Mars. We use the first 2580 martian sols, nearly 4 Mars years,of measurements to identify atmospheric pressure waves with periods of tens of minutes to hours using wavelet analysis on residual pressure after the tidal harmonics are removed. We find these waves have a clear diurnal cycle with strongest activity in the early morning and late evening and a seasonal cycle with the strongest waves in the second half of the martian year (Ls= 180-360°). The strongest such waves of the entire mission occurred during the Mars Year 34 global dust storm. Comparable atmospheric waves are identified using atmospheric modeling with the MarsWRF general circulation model in a “nested” high spatial resolution mode. With the support of the modeling, we find these waves best fit the expected properties of inertia-gravity waves with horizontal wavelengths of O(100s) of km. PLAIN LANGUAGE SUMMARY Measuring air pressure from the surface of Mars has revealed a wide variety of atmospheric phenomena. The Curiosity rover's record or surface air pressure is now the longest yet made on Mars.We use the first ~8 years of Curiosity's pressure observations to look for atmospheric waves with periods of tens of minutes to hours. We find these waves have a clear pattern in their daily behavior with the strongest activity in the early morning and late evening and a seasonal cycle with the strongest waves in the second half of the martian year (Northern hemisphere fall and winter). The strongest such waves occurred in 2018 during a global dust storm. We find comparable waves in atmospheric modeling. With the support of modeling, we find these waves best fit the expected properties of buoyancy waves forced by airflow over topography with horizontal wavelengths of 100-1000 km.

Scott D Guzewich↗
NASA NTRS2009

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

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.

Xu, Tian-Bing↗
NASA NTRS2018

Silicon Carbide Pressure Sensors for Venus Environment

We report on the evaluation of 4H-SiC piezoresistive pressure sensors in the simulated Venus environment of the NASA Glenn Extreme Environments Rig (GEER). The purpose of the evaluation was to determine the survivability of the pressure and temperature sensors and ancillary packaging components when subjected to the high pressure and aggressive chemical media that are characteristic of the Venus environment. Interest in Venus has been stimulated by the ongoing debate about Earth's planetary evolution, particularly in regards to its climate, and NASA has proposed a flagship mission to Venus to be launched in the near future. Quantifying how the Venus evo-lution ran its course will greatly aid researchers trying to model Earth's climate dynamics.

high temperature↗
DOE OSTI2022

Laboratory and In-Pile Testing of a Fiber Optic Pressure Sensor

The development, testing and deployment of a fiber-optic-based extrinsic Fabry-Perot pressure sensor is discussed. The details of design and fabrication procedure is discussed and the methodology for design decisions is provided. Results from laboratory-based testing and calibration is provided as-well-as preliminary data from in-pile testing in the Transient Reactor Test Facility.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1993

Development of a piezopolymer pressure sensor for a portable fetal heart rate monitor

A piezopolymer pressure sensor has been developed for service in a portable fetal heart rate monitor, which will permit an expectant mother to perform the fetal nonstress test, a standard predelivery test, in her home. Several sensors are mounted in an array on a belt worn by the mother. The sensor design conforms to the distinctive features of the fetal heart tone, namely, the acoustic signature, frequency spectrum, signal amplitude, and localization. The components of a sensor serve to fulfill five functions: signal detection, acceleration cancellation, acoustical isolation, electrical shielding, and electrical isolation of the mother. A theoretical analysis of the sensor response yields a numerical value for the sensor sensitivity, which is compared to experiment in an in vitro sensor calibration. Finally, an in vivo test on patients within the last six weeks of term reveals that nonstress test recordings from the acoustic monitor compare well with those obtained from conventional ultrasound.

Heart Rate, Fetal/physiology↗
NASA NTRS1995

Thermoelectric Control Of Temperatures Of Pressure Sensors

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.

Burkett, Cecil G., Jr.↗
NASA NTRS1987

Fiber-optic photoelastic pressure sensor with fiber-loss compensation

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.

Beheim, G.↗
NASA NTRS1972

Thin film oxygen partial pressure sensor

The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.

Wortman, J. J.↗
NASA NTRS2012

Temperature Induced Voltage Offset Drifts in Silicon Carbide Pressure Sensors

We report the reduction of transient drifts in the zero pressure offset voltage in silicon carbide (SiC) pressure sensors when operating at 600 C. The previously observed maximum drift of +/- 10 mV of the reference offset voltage at 600 C was reduced to within +/- 5 mV. The offset voltage drifts and bridge resistance changes over time at test temperature are explained in terms of the microstructure and phase changes occurring within the contact metallization, as analyzed by Auger electron spectroscopy and field emission scanning electron microscopy. The results have helped to identify the upper temperature reliable operational limit of this particular metallization scheme to be 605 C.

Okojie, Robert S.↗
NASA NTRS1970

Thin film devices used as oxygen partial pressure sensors

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.

Canady, K. S.↗
NASA NTRSDate not supplied

Evaluation of Silicon Carbide Pressure Sensor in Turbofan Engine Core Exhaust Nozzle

We report the results of the evaluation of single crystal 4H-silicon carbide piezoresistive pressure sensors that were directly inserted at the compressor and core exhaust nozzle exits, in shear contact with the engine-internal flow streams of the NASA DGEN Aeropropulsion Research Turbofan, where the operating temperatures at maximum power were ~230 oC, and ~460 oC, respectively. In addition to demonstrating sensor survivability during this maiden test, the frequency responses of the silicon-carbide sensors at the core-nozzle exit were compared against industry-standard silicon-based piezoresistive pressure transducers that externally placed, using an infinite-tube-probe arrangement. The low-voltage output of these early-development SiC sensors limited the frequency range with an acceptable signal-to-noise-ratio for the current application to less than about 2,500 Hz. The low output of the SiC sensors were due to a conservative burst-pressure diaphragm design that can be optimized to increase the frequency range. The results from this initial campaign offered insights to aspects of the sensor that would require further improvement, with the goal of achieving full-bandwidth capture of engine unsteady pressure fluctuations by direct interrogation of the flow field in hostile-environment engine-core components.

Silicon Carbide↗
NASA NTRSDate not supplied

Evaluation of SiC Pressure Sensors in Turbofan Engine Core Exhaust Nozzle

We report the results of the evaluation of single crystal 4H-silicon carbide piezoresistive pressure sensors that were directly inserted at the compressor and core exhaust nozzle exits, in shear contact with the engine-internal flow streams of the NASA DGEN Aeropropulsion Research Turbofan, where the operating temperatures at maximum power were ~230°C, and ~460°C, respectively. In addition to demonstrating sensor survivability during this maiden test, the frequency responses of the silicon-carbide sensors at the core-nozzle exit were compared against industry-standard silicon-based piezoresistive pressure transducers that externally placed, using an infinite-tube-probe arrangement. The low-voltage output of these early-development SiC sensors limited the frequency range with an acceptable signal-to-noise-ratio for the current application to less than about 2,500 Hz. The low output of the SiC sensors were due to a conservative burst-pressure diaphragm design that can be optimized to increase the frequency range. The results from this initial campaign offered insights to aspects of the sensor that would require further improvement, with the goal of achieving full-bandwidth capture of engine unsteady pressure fluctuations by direct interrogation of the flow field in hostile-environment engine-core components.

Silicon Carbide↗