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  • AERODYNAMICS  (5,077)
  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1985-1989  (4,390)
  • 1975-1979  (3,299)
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Years
Year
  • 1
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    Real time reflectometer (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A real time reflectometer with the particular utility of measuring fairly rapid (transient) changes in the specular reflectance of a sample which is continuously exposed to a perturbing environment is described. A fixed radiation source, a fixed detector, a uniformly rotating sample wheel, and a uniformly rotating optical wheel protect against misalignment problems. The reflectometer operates by comparing the measurings of a reflected signal with that of a reference signal made within fractions of a second of one another. Reflectance is measured in the infrared, visible, and vacuum ultraviolet regions.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    A new flow model for highly separated airfoil flows at low speeds (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An analytical model for separated airfoil flows is presented which is based on experimentally observed physical phenomena. These include a free stagnation point aft of the airfoil and a standing vortex in the separated region. A computer program is described which iteratively matches the outer potential flow, the airfoil turbulent boundary layer, the separated jet entrainment, mass conservation in the separated bubble, and the rear stagnation pressure. Separation location and pressure are not specified a priori. Results are presented for surface pressure coefficient and compared with experiment for three angles of attack for a GA(W)-1, 17% thick airfoil.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Advanced Technol. Airfoil Res., Vol. 1, Pt. 1; p 367-382
    Format: application/pdf
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  • 3
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    Fiber optic sensor for measurement of pressure fluctuations at high temperatures (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A fiber-optic sensor, based on the principle of the fiber-optic lever, is described which features small size, extended bandwidth, and capability to operate at high temeratures, as required for measurements in hypersonic flow. The principle of operation, design features peculiar to the intended application, and expected performance at high temperatures are described.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ICIASF ''89; Sept. 18-21, 1989; Goettingen; Germany
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Ultrasonic level sensors for liquids under high pressure (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: 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.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 57; 2318-232
    Format: text
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  • 5
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    A high-temperature wideband pressure transducer (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Progress in the development of a pressure transducer for measurement of the pressure fluctuations in the high temperature environment of a jet exhaust is reported. A condenser microphone carrier system was adapted to meet the specifications. A theoretical analysis is presented which describes the operation of the condenser microphone in terms of geometry, materials, and other physical properties. The analysis was used as the basis for design of a prototype high temperature microphone. The feasibility of connecting the microphone to a converter over a high temperature cable operating as a half-wavelength transmission line was also examined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-145710 , PGS-TR-PH-75-16
    Format: application/pdf
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  • 6
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    Instrumentation for measurement of aircraft noise and sonic boom (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A jet aircraft noise and sonic boom measuring device which converts sound pressure into electric current is described. An electric current proportional to the sound pressure level at a condenser microphone is produced and transmitted over a cable, amplified by a zero drive amplifier and recorded on magnetic tape. The converter is comprised of a local oscillator, a dual-gate field-effect transistor (FET) mixer and a voltage regulator/impedance translator. A carrier voltage that is applied to one of the gates of the FET mixer is generated by the local oscillator. The microphone signal is mixed with the carrier to produce an electrical current at the frequency of vibration of the microphone diaphragm by the FET mixer. The voltage of the local oscillator and mixer stages is regulated, the carrier at the output is eliminated, and a low output impedance at the cable terminals is provided by the voltage regulator/impedance translator.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 7
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    Theoretical response of condenser microphones (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Modifications to prior theory yield expressions for the frequency response and equivalent lumped elements of a condenser microphone in terms of its fundamental geometrical and material properties. Results of the analysis show excellent agreement with experimental data taken on B&K pressure microphone types 4134 and 4146.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Acoustical Society of America; vol. 64
    Format: text
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  • 8
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    A high-temperature wideband pressure transducer (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A condenser microphone AM carrier system, which has been developed to measure pressure fluctuations at elevated temperatures, consists of the following components: a condenser microphone designed for operation at elevated temperatures; existing carrier electronics developed under two previous research grants but adapted to meet present requirements; a 6 m cable operating as a half-wavelength transmission line between the microphone and carrier electronics; and a voltage-controlled oscillator used in a feedback loop for automatic tuning control. Both theoretical and practical aspects of the development program are considered. The three predominant effects of temperature changes are changes in the membrane-backplate gap, membrane tension, and air viscosity. The microphone is designed so that changes in gap and membrane tension tend to have compensating effects upon the microphone sensitivity.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-149789 , PGSTR-PH77-48
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  • 9
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    A high-temperature wideband pressure transducer (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The problem of operating a condenser microphone as a terminal element of a half wavelength transmission line was dealt with; the environment in which the microphone operates necessitates a 25 foot separation from its supporting electronics. A theoretical analysis of the microphone-cable system, substantiated by laboratory tests, provided criteria to optimize system gain.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-146422 , PGSTR-PH76-24
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  • 10
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    Measurement of Seebeck coefficient using a light pulse (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X-Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X-Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than + or - 1 percent.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 56; 719-722
    Format: text
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