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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Pulse transducer with artifact signal attenuator

An artifact signal attenuator for a pulse rate sensor is described. The circuit for attenuating background noise signals is connected with a pulse rate transducer which has a light source and a detector for light reflected from blood vessels of a living body. The heart signal provided consists of a modulated dc signal voltage indicative of pulse rate. The artifact signal resulting from light reflected from the skin of the body comprises both a constant dc signal voltage and a modulated dc signal voltage. The amplitude of the artifact signal is greater and the frequency less than that of the heart signal. The signal attenuator circuit includes an operational amplifier for canceling the artifact signal from the output signal of the transducer and has the capability of meeting packaging requirements for wrist-watch-size packages.

Cash, W. H., Jr.↗
NASA NTRS1982

Lightweight, Low-Loss dc Transducer

Direct current is measured by lightweight, magnetically coupled transducer that weighs only 4 grams, without actually being wired into circuit under test. Miniature dc transducer has five windings: 2 for ac excitation inputs, 2 for dc control inputs, and 1 for feedback. Wire gages are selected for minimum size and weight. Size and number of turns of dc windings are selected according to dc current range to be measured.

Nagano, S.↗
NASA NTRS1981

Multifunctional transducer

Several parameters of a small region of a muscle tissue or other object, can be simultaneously measured using with minimal traumatizing or damage of the object, a trifunctional transducer which can determine the force applied by a muscle fiber, the displacement of the fiber, and the change in thickness of the fiber. The transducer has three legs with inner ends joined together and outer ends formed to piece the tissue and remain within it. Two of the legs are relatively stiff, to measure force applied by the tissue, and a third leg is relatively flexible to measure displacement of the tissue relative to one or both stiff legs, and with the three legs lying in a common plane so that the force and displacement measurements all relate to the same direction of muscle movements. A flexible loop is attached to one of the stiff legs to measure changes in muscle thickness, with the upper end of the loop fixed to the leg and the lower end of the loop bearing against the surface of the tissue and being free to slide on the leg.

Feldstein, C.↗
NASA NTRS1981

Photomechanical transducer

Light absorbing ultra-thin films mounted under a fixed strain exhibit the behavior of an optomechanicalor photomechanical transducer. The transducer responds to light in a quick and reversible manner converting a time-variable light source into a time-variable mechanical stress easily monitored by a device such as a strain gage.

Fedors, R. F.↗
NASA NTRS1982

Ultrasonic input-output for transmitting and receiving longitudinal transducers coupled to same face of isotropic elastic plate

The quantitative understanding of ultrasonic nondestructive evaluation parameters such as the stress wave factor were studied. Ultrasonic input/output characteristics for an isotropic elastic plate with transmitting and receiving longitudinal transducers coupled to the same face were analyzed. The asymptotic normal stress is calculated for an isotropic elastic half space subjected to a uniform harmonic normal stress applied to a circular region at the surface. The radiated stress waves are traced within the plate by considering wave reflections at the top and bottom faces. The output voltage amplitude of the receiving transducer is estimated by considering only longitudinal waves. Agreement is found between the output voltage wave packet amplitudes and times of arrival due to multiple reflections of the longitudinal waves.

Williams, J. H., Jr.↗
NASA NTRS1982

Hot foil transducer skin friction sensor

The device utilizes foil transducers with only one edge exposed to the fluid flow. The surfaces are polished producing a foil transducer that does not generate turbulence while sufficiently thick to carry the required electrical current for high temperature fluid flow. The assembly utilizes a precut layered metal sandwich with attached electrodes eliminating a need for welding and individual sensor calibration.

Vranas, T.↗
NASA NTRS1985

Transducers For Heat Research

Series of transducers with seven different configurations enable measurement of forces and displacements in heart wall. New transducers small, cause minimal perturbation of heart function and attached and detached without causing excessive tissue damage. All units implanted or removed during single heartbeat, permitting rapid relocation for detail mapping.

Feldstein, C.↗
NASA NTRS1985

Multipurpose Photonic Transducers

Features include smallness and noise immunity. Photonic transducer is interferometer with two arms. Small relative axial motions of mirrors detected as shifts in interference pattern. Version measures temperature changes via differential expansion or contraction of stalks. New transducers smaller (typical size less than 1 cm) and coupled to monitoring equipment with optical fibers instead of wires. Well suited to biomedical instrumentation.

Du Fresne, E. R.↗
NASA NTRS1985

Fabricating Underwater Electroacoustic Transducers

Use of retainer ring instead of adhesives simplifies assembly and disassembly. Underwater electroacoustical transducer assembly uses precast silicone rubber compressed between ceramic crystal and metal container. Removable retainer ring holds assembly in place. Method provides proper stress loading, speed and ease of assembly, and way of removing transducer without damaging crystal.

Ferguson, R. L.↗
NASA NTRS1983

Ultrasonic transducer with a two-dimensional Gaussian field profile

A transducer is described which generates a two-dimensional Gaussian field by controlling both the position of multiple circular electrodes and the voltage applied to each electrode. The transducer is constructed by depositing concentric rings electrodes onto one flat surface of a circular piezoelectric crystal disk and attaching the rings to an impedance matching network which acts as a voltage divider. Geometrical inter-ring separations and electrical inter-ring impedances are designed to minimize the error between the generated acoustic field, modeled as a piecewise linear function, and the desired Gaussian distribution. Total mean squared error between the averaged far-field data and a Gaussian shape is less than two percent.

Claus, R. O.↗
NASA NTRS1985

Spring-Loaded Transducer Holder

Portable ultrasonic scanner moves transducer at constant pressure. Spring-loaded holder moves ultrasonic transducer over test sample at constant pressure. Setup used to determine rate of debond taking place in glued materials subjected to fatigue loading. Holder designed as portable field unit adapted to fatigue machine that transmits data while specimen tested.

Gardner, M. R.↗
NASA NTRS1986

Calibrating Pressure Transducers at Cryogenic Temperatures

To calibrate transducers immersed in cryogenic environment, sealed reciprocating bellows generates sinusoidal dynamic pressure. Transducer manifold assembly and bellows immersed in cryogenic environment to minimize gradients in controllable cryogenic temperature.

Gibbens, B. V.↗
NASA NTRS1985

An advanced solid state pressure transducer for high reliability SSME application

New methods to advance the state-of-the-art of pressure sensors for the Space Shuttle Main Engine were demonstrated. The results of the feasibility and breadboard demonstration phase and the current status of the research development prototype follow-on phase are presented. A technology breakthrough utilizing silicon piezoresistive technology was achieved in the first phase. A transducer design concept for the SSME application utilizes packaging materials with similar thermal coefficients of expansion and maintains the transducer seals primarily in compression. The silicon chip design will provide dual sensing outputs with laser trimmable integrated compensating electronics. The silicon resistor ion implant dose was customized for the SSME temperature requirement. A basic acoustic modeling software program was developed to evaluate the frequency response characteristics for the package design.

Johnson, R. L.↗
NASA NTRS1983

A thin film strain transducer

A device has been developed for the purpose of measuring longitudinal strain in thin polyethylene films. This paper describes the design, development, calibration, and application of this unique transducer in a variety of low temperature environments. This thin, ring-shaped device has a low effective modulus so as not to interfere with the strain that would naturally occur in a thin film. It has a standard 350 ohm impedance which is compatible with most available bridge balance, amplification, and telemetry instrumentation. This transducer has been successfully used for viscoelastic material characterization experiments in the laboratory, as well as in flight measurements of strain on the surface of scientific balloons during inflation, launch, ascent, and float.

Rand, J. L.↗
NASA NTRS1984

How to design and construct multielement ultrasonic transducers

The practical 'how to' design and construction of multielement ultrasonic transducers are described. First, design procedures based on direct calculations of the desired acoustic field are reviewed. Second, techniques for implementing these designs using piezoelectric active elements are discussed. Finally, optical and acoustic test methods for transducer calibration are indicated.

Burrier, R. A.↗
NASA NTRS1987

Pressure-Transducer Simulator

Simulation circuit operates under remote, automatic, or manual control to produce electrical outputs similar to pressure transducer. Specific circuit designed for simulations of Space Shuttle main engine. General circuit concept adaptable to other simulation and control systems involving several operating modes. Switches and amplifiers respond to external control signals and panel control settings to vary differential excitation of resistive bridge. Output voltage or passive terminal resistance made to equal pressure transducer in any of four operating modes.

Simon, Richard A.↗
NASA NTRS1986

Supplementary calibration test of the tip-aerodynamics- and acoustics-test pressure transducers

A calibration test is described that was performed to supplement the normal calibration of the 188 pressure transducers used in the Tip Aerodynamics and Acoustics Test. This calibration led to the identification of 15 transducers which had a slope change of greater than 7% from the initial calibration. The calibration procedure is described and the results presented. The effect of the slope changes on the pressure distributions are described, followed by a method to compensate for these changes.

Watts, M. E.↗
NASA NTRS1988

Calibrating Nonremovable Pressure Transducers

Report describes supplementary calibration procedure for pressure transducers. Method developed for transducers that cannot be removed without damage. Units calibrated en masse in large pressure chamber.

Watts, Michael E.↗