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Results for “measurement errors”

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 523 records · Page 29

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NASA NTRS1976

A microprocessor controlled pressure scanning system

A microprocessor-based controller and data logger for pressure scanning systems is described. The microcomputer positions and manages data from as many as four 48-port electro-mechanical pressure scanners. The maximum scanning rate is 80 pressure measurements per second (20 ports per second on each of four scanners). The system features on-line calibration, position-directed data storage, and once-per-scan display in engineering units of data from a selected port. The system is designed to be interfaced to a facility computer through a shared memory. System hardware and software are described. Factors affecting measurement error in this type of system are also discussed.

Anderson, R. C.↗

NASA NTRS1976

Experimental investigation to validate use of cryogenic temperatures to achieve high Reynolds numbers in boattail pressure testing

An investigation has been conducted in the Langley 1/3 meter transonic cryogenic tunnel to validate the use of cryogenic temperatures to achieve high Reynolds numbers in nozzle boattail pressure testing. Tests were conducted at 0 degree angle of attack and at Mach numbers of 0.60, 0.85, and 0.90 on two wing-body configurations with differing boattail geometries. Test data were obtained by using two different techniques, the cryogenic method and the conventional method, to obtain the same Reynolds number. Later, the test data obtained from the two techniques on boattail pressure coefficient distributions and pressure drag coefficients were compared; results from the comparisons show excellent repeatability for all test conditions and indicate no measurable errors when using cryogenic temperatures to achieve high Reynolds numbers for nozzle boattail pressure testing.

Reubush, D. E.↗

NASA NTRS1975

Development of TPS flight test and operational instrumentation

Thermal and flow sensor instrumentation was developed for use as an integral part of the space shuttle orbiter reusable thermal protection system. The effort was performed in three tasks: a study to determine the optimum instruments and instrument installations for the space shuttle orbiter RSI and RCC TPS; tests and/or analysis to determine the instrument installations to minimize measurement errors; and analysis using data from the test program for comparison to analytical methods. A detailed review of existing state of the art instrumentation in industry was performed to determine the baseline for the departure of the research effort. From this information, detailed criteria for thermal protection system instrumentation were developed.

Carnahan, K. R.↗

NASA NTRS1976

Softwall acoustical characteristics and measurement capabilities of the NASA Lewis 9x15 foot low speed wind tunnel

Acoustical characteristics and source directionality measurement capabilities of the wind tunnel in the softwall configuration were evaluated, using aerodynamically clean microphone supports. The radius of measurement was limited by the size of the test section, instead of the 3.0 foot (1 m) limitation of the hardwall test section. The wind-on noise level in the test section was reduced 10 dB. Reflections from the microphone support boom, after absorptive covering, induced measurement errors in the lower frequency bands. Reflections from the diffuser back wall were shown to be significant. Tunnel noise coming up the diffuser was postulated as being responsible, at least partially, for the wind-on noise in the test section and settling chamber. The near field characteristics of finite-sized sources and the theoretical response of a porous strip sensor in the presence of wind are presented.

Rentz, P. E.↗

NASA NTRS1975

Meter-wavelength VLBI. II - The observations

Observations made during a series of meter-wavelength very-long-baseline (VLBI) experiments conducted during 1971-1973 are reported. A wide variety of objects was observed, including many extragalactic sources known to have compact components, several strong pulsars (especially the Crab nebula pulsar), and a selection of supernova remnants. The experiments are discussed in detail, and tests made to check the consistency of the results are described. The measured correlated flux densities are presented for each source as a function of interferometer baseline and observing frequency. An assessment is made of the measurement errors and of the possibility of confusion within the interferometer beam. The results show that all sources except the pulsars, which are known to have intrinsically small sizes, are resolved on the longest baseline. We also conclude that no supernova remnants except the Crab nebula and Cassiopeia A gave evidence of compact components.

Clark, T. A.↗

NASA NTRS1976

Test of the principle of operation of a wideband magnetic direction finder for lightning return strokes

The principle of operation of a wideband crossed-loop magnetic-field direction finder is studied by comparing the bearing determined from the NS and EW magnetic fields at various times up to 155 microsec after return stroke initiation with the TV-determined lightning channel base direction. For 40 lightning strokes in the 3 to 12 km range, the difference between the bearings found from magnetic fields sampled at times between 1 and 10 microsec and the TV channel-base data has a standard deviation of 3-4 deg. Included in this standard deviation is a 2-3 deg measurement error. For fields sampled at progressively later times, both the mean and the standard deviation of the difference between the direction-finder bearing and the TV bearing increase. Near 150 microsec, means are about 35 deg and standard deviations about 60 deg. The physical reasons for the late-time inaccuracies in the wideband direction finder and the occurrence of these effects in narrow-band VLF direction finders are considered.

Herrman, B. D.↗

NASA NTRS1976

Regions of constrained maximum likelihood parameter identifiability

This short paper considers the parameter-identification problem of general discrete-time, nonlinear, multiple input-multiple output dynamic systems with Gaussian white distributed measurement errors. Knowledge of the system parameterization is assumed to be available. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems.

Lee, C.-H.↗

NASA NTRS1976

Navigation accuracy analysis for the Mariner-Jupiter-Saturn 1977 mission

The results of the latest navigation capability study for the Mariner-Jupiter-Saturn 1977 mission are presented and analyzed. Predicted planet-relative and satellite-relative accuracies are given for radio only and radio plus optical approach navigation on three representative trajectories. In addition, planet-relative accuracies are given for cruise navigation on one of the trajectories. The dynamical and measurement error models used in the study are discussed, and the basic MJS77 navigation strategy is described. The navigation capability is evaluated in the light of the mission's objectives; and the variation in capability among the three trajectories is examined with regard to the effects of the major error sources and the trajectory dependent encounter geometries.

Jacobson, R. A.↗

NASA NTRS1976

Laboratory calibration of AAFE radiometer/scatterometer (RADSCAT)

A brief description of the electrical and mechanical instrument configuration, followed by an extensive discussion of laboratory tests and results are contained herein. This information is required to provide parameters for data reduction, and a basis for analysis of the measurement errors in data taken with this instrument.

Schroeder, L. C.↗

NASA NTRS1977

Load-displacement measurement and work determination in three-point bend tests of notched or precracked specimens

Suggestions for testing of notched or cracked three-point bend specimens are presented which: (1) correct displacement measurement errors resulting from misalignment between the load applicator and specimen; (2) account for coincidental strains not associated with the work of crack extension; (3) simplify record analysis and processing; and (4) extend displacement gage range without sacrifice of sensitivity or accuracy. These testing details are particularly applicable to procedures in which the crack extension force is determined from the work done on the specimen.

Buzzard, R. J.↗

NASA NTRS1977

Pseudo noise test set operation manual

Pseudonoise (PN) test set was designed to provide a reliable, operationally simple unit which allows the previously mentioned analog rms end-to-end error measurement of most communication systems to be easily performed. It also provides a band-limited pseudorandom noise as input, thereby escaping the disadvantages of most deterministic signals while retaining the advantages of using true-band-limited noise. In addition, the PN test set has the capability to be used as a means with which the autocorrelation function and impulse response may be determined for certain systems.

Weathers, G.↗

NASA NTRS1977

The mean magnetic field of the sun: Observations at Stanford

A solar telescope was built at Stanford University to study the organization and evolution of large-scale solar magnetic fields and velocities. The observations are made using a Babcock-type magnetograph which is connected to a 22.9 m vertical Littrow spectrograph. Sun-as-a-star integrated light measurements of the mean solar magnetic field were made daily since May 1975. The typical mean field magnitude is about 0.15 gauss with typical measurement error less than 0.05 gauss. The mean field polarity pattern is essentially identical to the interplanetary magnetic field sector structure (seen near the earth with a 4 day lag). The differences in the observed structures can be understood in terms of a warped current sheet model.

Scherrer, P. H.↗

NASA NTRS1977

Least squares polynomial fits and their accuracy

Equations are presented which attempt to fit least squares polynomials to tables of date. It is concluded that much data are needed to reduce the measurement error standard deviation by a significant amount, however at certain points great accuracy is attained.

Lear, W. M.↗

NASA NTRS1975

Regions of constrained maximum likelihood parameter identifiability

This paper considers the parameter identification problem of general discrete-time, nonlinear, multiple-input/multiple-output dynamic systems with Gaussian-white distributed measurement errors. Knowledge of the system parameterization is assumed to be known. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems. It is shown that if the vector of true parameters is locally CML identifiable, then with probability one, the vector of true parameters is a unique maximal point of the maximum likelihood function in the region of parameter identifiability and the CML estimation sequence will converge to the true parameters.

Lee, C.-H.↗

NASA NTRS1976

A microprocessor controlled pressure scanning system

Anderson, R. C.↗

NASA NTRS1977

Maximum theoretical angular accuracy of planar and linear arrays of sensors

The maximum theoretical accuracy in the angular location of a radiating object that can be obtained by using a planar or linear array is studied. The elements are assumed to have identical radiation patterns and the complex voltages observed at their ports are assumed to be subject to phase measurement errors, having normal probability density. An optimum scheme for the statistical extraction of the parameters defining the direction is established noting that the presence of thermal noise does not affect the structure of the estimator. Comparisons with the conventional multiple interferometric techniques are made.

Borgiotti, G. V.↗

NASA NTRS1979

Cosine-corrected optical diffuser

In solar energy utilization studies, correct measurements of flux arriving at other angles to optical axis must be given. Developed device (Cosine diffuser) significantly reduces measurement errors. In combination of radiation transmitter and diffuser co-operating with collimated optical instrument, relative aperture of instrument is filled.

Estey, R. S.↗

NASA NTRS1977

Nucleonic coal detector with independent, hydropneumatic suspension

The design of a nucleonic, coal interface detector which measures the depth of coal on the roof and floor of a coal mine is presented. The nucleonic source and the nucleonic detector are on independent hydropneumatic suspensions to reduce the measurement errors due to air gap.

Jones, E. W.↗