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  • 1
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    Summary Report of the First International Symposium on Strain Gauge Balances and Workshop on AoA/Model Deformation Measurement Techniques (1998)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: The first International Symposium on Strain Gauge Balances was sponsored under the auspices of the NASA Langley Research Center (LaRC), Hampton, Virginia. Held at the LaRC Reid Conference Center, the Symposium provided an open international forum for presentation, discussion, and exchange of technical information among wind tunnel test technique specialists and strain gauge balance designers. The Symposium also served to initiate organized professional activities among the participating and relevant international technical communities. The program included a panel discussion, technical paper sessions, tours of local facilities, and vendor exhibits. Over 130 delegates were in attendance from 15 countries. A steering committee was formed to plan a second international balance symposium tentatively scheduled to be hosted in the United Kingdom in 1998 or 1999. The Balance Symposium was followed bv the half-day, Workshop on Angle of Attack and Model Deformation on the afternoon of October 25. The thrust of the Workshop was to assess the state of the art in angle of attack (AoA) and model deformation measurement techniques and to discuss future developments.
    Keywords: Instrumentation and Photography
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  • 2
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    An improved calibration technique for wind tunnel model attitude sensors (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Aerodynamic wind tunnel tests at NASA Langley Research Center (LaRC) require accurate measurement of model attitude. Inertial accelerometer packages have been the primary sensor used to measure model attitude to an accuracy of +/- 0.01 deg as required for aerodynamic research. The calibration parameters of the accelerometer package are currently obtained from a seven-point tumble test using a simplified empirical approximation. The inaccuracy due to the approximation exceeds the accuracy requirement as the misalignment angle between the package axis and the model body axis increases beyond 1.4 deg. This paper presents the exact solution derived from the coordinate transformation to eliminate inaccuracy caused by the approximation. In addition, a new calibration procedure is developed in which the data taken from the seven-point tumble test is fit to the exact solution by means of a least-squares estimation procedure. Validation tests indicate that the new calibration procedure provides +/- 0.005-deg accuracy over large package misalignments, which is not possible with the current procedure.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: International Instrumentation Symposium, 39th, Albuquerque, NM, May 2-6, 1993, Proceedings (A93-54351 24-35); p. 89-102.
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  • 3
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    Preliminary Statistical Analysis of the 1995 Evaluation by NASA LaRC of the IAI Automatic Balance Calibration Machine (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The NASA Langley Research Center (LARC) participated in a national cooperative evaluation of the Israel Aircraft Industries (IAI) automatic balance calibration machine at Microcraft, San Diego in September 1995. A LaRC-designed six-component strain gauge balance was selected for test and calibration during LaRC's scheduled evaluation period. Eight calibrations were conducted using three selected experimental designs. Raw data were exported to LaRC facilities for reduction and statistical analysis using the techniques outlined in Tripp and Tcheng (1994). This report presents preliminary assessments of the results, and compares IAI calibration results with manual calibration results obtained at the Modern Machine and Tool Co., Inc. (MM & T). Newport News, VA. A more comprehensive report is forthcoming.
    Keywords: Instrumentation and Photography
    Type: First International Symposium on Strain Gauge Balances; Pt. 1; 353-371; NASA/CP-1999-209101/PT1
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  • 4
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    A miniature remote deadweight calibrator (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A miniature, computer-controlled, deadweight calibrator was developed to remotely calibrate a force transducer mounted in a cryogenic chamber. This simple mechanism allows automatic loading and unloading of deadweights placed onto a skin friction balance during calibrations. Equipment for the calibrator includes a specially designed set of five interlocking 200-milligram weights, a motorized lifting platform, and a controller box taking commands from a microcomputer on an IEEE interface. The computer is also used to record and reduce the calibration data and control other calibration parameters. The full-scale load for this device is 1,000 milligrams; however, the concept can be extended to accommodate other calibration ranges.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 5
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    Super magnets for large tunnels (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The development and use of a large Magnetic Suspension and Balance System (MSBS) in wind tunnels is examined, discussing NASA-sponsored research to develop a large MSBS, and the 2 MSBS already in use. The MSBS holds the model in an arbitrary position in the wind tunnel test section and measures the forces and moments acting on the model. Technologies for building a large MSBS have been developed, and research is being done to reduce building costs. Magnetic suspension is advantageous because it completely eliminates interference from mechanical support systems such as stings or struts and it allows for easy rotation and translation of the model. Advances allowing operation at higher temperatures, probably using liquid nitrogen instead of liquid helium may reduce the cost of MSBS operation. A large MSBS would require power controllers with capacity up to 10 MW, efficiency approaching 98 percent and the ability to reverse the sign of both voltage and current. Technologies include the electro-magnetic position sensor, model positioning sensing, digital controller, and a precalibrated resistance strain-gage balance.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: Aerospace America (ISSN 0740-722X); 26; 36
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  • 6
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    Surgical force detection probe (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The development progress of a precision electro-mechanical instrument which allows the detection and documentation of the forces and moment applied to human tissue during surgery (under actual operation room conditions), is reported. The pen-shaped prototype probe which measures 1/2 inch in diameter and 7 inches in length was fabricated using an aerodynamic balance. The aerodynamic balance, a standard wind tunnel force and moment sensing transducer, measures the forces and the moments transmitted through the surgeon's hand to the human tissue during surgery. The prototype probe which was fabricated as a development tool was tested successfully. The final version of the surgical force detection probe will be designed based on additional laboratory tests in order to establish the full scale loads. It is expected that the final product will require a simplified aerodynamic balance with two or three force components and one moment component with lighter full scale loads. A signal conditioner was fabricated to process and display the outputs from the prototype probe. This unit will be interfaced with a PC-based data system to provide automatic data acquisition, data processing, and graphics display. The expected overall accuracy of the probe is better than one percent full scale.
    Keywords: AEROSPACE MEDICINE
    Type: NASA, Washington, Technology 2001: The Second National Technology Transfer Conference and Exposition, Volume 2; p 518-532
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  • 7
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    Summary Report of the First International Symposium on Strain Gauge Balances and Workshop on AoA/Model Deformation Measurement Techniques (1999)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The first International Symposium on Strain Gauge Balances was sponsored under the auspices of the NASA Langley Research Center (LaRC), Hampton, Virginia during October 22-25, 1996. Held at the LaRC Reid Conference Center, the Symposium provided an open international forum for presentation, discussion, and exchange of technical information among wind tunnel test technique specialists and strain gauge balance designers. The Symposium also served to initiate organized professional activities among the participating and relevant international technical communities. The program included a panel discussion, technical paper sessions, tours of local facilities, and vendor exhibits. Over 130 delegates were in attendance from 15 countries. A steering committee was formed to plan a second international balance symposium tentatively scheduled to be hosted in the United Kingdom in 1998 or 1999. The Balance Symposium was followed by the half-day Workshop on Angle of Attack and Model Deformation on the afternoon of October 25. The thrust of the Workshop was to assess the state of the art in angle of attack (AoA) and model deformation measurement techniques and to discuss future developments.
    Keywords: Instrumentation and Photography
    Type: First International Symposium on Strain Gauge Balances; Pt. 2; 727-738; NASA/CP-1999-209101/PT2
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  • 8
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    Status of magnetic suspension technology (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The reasons for the continuing interest in the Magnetic Suspension and Balance System (MSBS) are highlighted. Typical problems that can arise because of model-support interference in a transonic wind tunnel are shown to illustrate the need for MSBS. The two magnetic suspension systems in operation at Langley are the only ones active in the U.S. One of these systems is the 13 inch MSBS which was borrowed from the Air Force Arnold Engineering Development Center. The other system is the 6 inch MSBS which was developed by MIT Aerophysics Laboratory with NASA and DOD funding. Each of these systems is combined with a subsonic wind tunnel. Ongoing research in both of these systems is covered. Last year, Madison Magnetics, Inc., completed a contractual design and cost study utilizing some advance concepts for a large MSBS which would be compatible with an 8 foot transonic wind tunnel and the highlights of the study are presented. Sverdrup Technology, Inc., recently performed a study under contract for Langley on the potential usefulness to the aerospace industry of a proposed large MSBS combined with a suitable transonic wind tunnel. The results of that study are discussed. Langley has partially funded the MSBS work at the University of Southampton for about 6 years under a grant arrangement and the major results are summarized.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: Langley Symposium on Aerodynamics, Volume 1; p 261-277
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  • 9
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    Characterization and Uncertainty Analysis of a Reference Pressure Measurement System for Wind Tunnels (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: This paper presents the calibration results and uncertainty analysis of a high-precision reference pressure measurement system currently used in wind tunnels at the NASA Langley Research Center (LaRC). Sensors, calibration standards, and measurement instruments are subject to errors due to aging, drift with time, environment effects, transportation, the mathematical model, the calibration experimental design, and other factors. Errors occur at every link in the chain of measurements and data reduction from the sensor to the final computed results. At each link of the chain, bias and precision uncertainties must be separately estimated for facility use, and are combined to produce overall calibration and prediction confidence intervals for the instrument, typically at a 95% confidence level. The uncertainty analysis and calibration experimental designs used herein, based on techniques developed at LaRC, employ replicated experimental designs for efficiency, separate estimation of bias and precision uncertainties, and detection of significant parameter drift with time. Final results, including calibration confidence intervals and prediction intervals given as functions of the applied inputs, not as a fixed percentage of the full-scale value are presented. System uncertainties are propagated beginning with the initial reference pressure standard, to the calibrated instrument as a working standard in the facility. Among the several parameters that can affect the overall results are operating temperature, atmospheric pressure, humidity, and facility vibration. Effects of factors such as initial zeroing and temperature are investigated. The effects of the identified parameters on system performance and accuracy are discussed.
    Keywords: Instrumentation and Photography
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  • 10
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    High-precision buffer circuit for suppression of regenerative oscillation (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Precision analog signal conditioning electronics have been developed for wind tunnel model attitude inertial sensors. This application requires low-noise, stable, microvolt-level DC performance and a high-precision buffered output. Capacitive loading of the operational amplifier output stages due to the wind tunnel analog signal distribution facilities caused regenerative oscillation and consequent rectification bias errors. Oscillation suppression techniques commonly used in audio applications were inadequate to maintain the performance requirements for the measurement of attitude for wind tunnel models. Feedback control theory is applied to develop a suppression technique based on a known compensation (snubber) circuit, which provides superior oscillation suppression with high output isolation and preserves the low-noise low-offset performance of the signal conditioning electronics. A practical design technique is developed to select the parameters for the compensation circuit to suppress regenerative oscillation occurring when typical shielded cable loads are driven.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-4658 , L-17453 , NAS 1.15:4658
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