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  • 1
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    An improved method for determining force balance calibration accuracy (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The results of an improved statistical method used at Langley Research Center for determining and stating the accuracy of a force balance calibration are presented. The application of the method for initial loads, initial load determination, auxiliary loads, primary loads, and proof loads is described. The data analysis is briefly addressed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: International Instrumentation Symposium, 39th, Albuquerque, NM, May 2-6, 1993, Proceedings (A93-54351 24-35); p. 321-335.
    Format: text
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  • 2
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    Cryogenic balances for the US NTF (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Force balances were used to obtain aerodynamic data in the National Transonic Facility (NTF) wind tunnel since it became operational in 1983. These balances were designed, fabricated, gaged, and calibrated to Langley Research Center's specifications to operate over the temperature range of -320 F to +140 F without thermal control. Some of the materials and procedures developed to obtain a balance that would perform in this environment are reviewed. The degree of success in using these balances thus far is reported. Some of the problem areas that need additional work are specified and some of the progress addressing these problems is described.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: AGARD, Special Course on Advances in Cryogenic Wind Tunnel Technology; 10 p
    Format: text
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  • 3
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    Automatic force balance calibration system (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A system for automatically calibrating force balances is provided. The invention uses a reference balance aligned with the balance being calibrated to provide superior accuracy while minimizing the time required to complete the calibration. The reference balance and the test balance are rigidly attached together with closely aligned moment centers. Loads placed on the system equally effect each balance, and the differences in the readings of the two balances can be used to generate the calibration matrix for the test balance. Since the accuracy of the test calibration is determined by the accuracy of the reference balance and current technology allows for reference balances to be calibrated to within +/-0.05% the entire system has an accuracy of +/-0.2%. The entire apparatus is relatively small and can be mounted on a movable base for easy transport between test locations. The system can also accept a wide variety of reference balances, thus allowing calibration under diverse load and size requirements.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NAS 1.71:LAR-15362-1
    Format: application/pdf
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  • 4
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    Aerodynamic measurements and thermal tests of a strain-gage balance in a cryogenic wind tunnel (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An internal strain-gage balance designed and constructed in Europe for use in cryogenic wind tunnels has been tested in the Langley 0.3-Meter Transonic Cryogenic Tunnel. Part of the evaluation was made at equilibrium balance temperatures and it consisted of comparing the data taken at a tunnel stagnation temperature of 300 K with the data taken at 200 K and 110 K while maintaining either the Reynolds number or the stagnation pressure. A sharp-leading-edge delta-wing model was used to provide the aerodynamic loading for these tests. Results obtained with the balance during the force tests were found to be accurate and repeatable both with and without the use of a convection shield on the balance. An additional part of this investigation involved obtaining data on the transient temperature response of the balance during both normal and rapid changes in the tunnel stagnation temperature. The variation of the temperature with time was measured at three locations on the balance near the physical locations of the strain gages. The use of a convection shield significantly increased the time required for the balance to stabilize at a new temperature during the temperature response tests.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-89039 , L-16208 , NAS 1.15:89039
    Format: application/pdf
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  • 5
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    Automatic force balance calibration system (1996)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: A system for automatically calibrating force balances is provided. The invention uses a reference balance aligned with the balance being calibrated to provide superior accuracy while minimizing the time required to complete the calibration. The reference balance and the test balance are rigidly attached together with closely aligned moment centers. Loads placed on the system equally effect each balance, and the differences in the readings of the two balances can be used to generate the calibration matrix for the test balance. Since the accuracy of the test calibration is determined by the accuracy of the reference balance and current technology allows for reference balances to be calibrated to within .+-.0.05%, the entire system has an accuracy of a .+-.0.2%. The entire apparatus is relatively small and can be mounted on a movable base for easy transport between test locations. The system can also accept a wide variety of reference balances, thus allowing calibration under diverse load and size requirements.
    Keywords: Instrumentation and Photography
    Format: application/pdf
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  • 6
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    Monitoring dynamic loads on wind tunnel force balances (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Two devices have been developed at NASA Langley to monitor the dynamic loads incurred during wind-tunnel testing. The Balance Dynamic Display Unit (BDDU), displays and monitors the combined static and dynamic forces and moments in the orthogonal axes. The Balance Critical Point Analyzer scales and sums each normalized signal from the BDDU to obtain combined dynamic and static signals that represent the dynamic loads at predefined high-stress points. The display of each instrument is a multiplex of six analog signals in a way that each channel is displayed sequentially as one-sixth of the horizontal axis on a single oscilloscope trace. Thus this display format permits the operator to quickly and easily monitor the combined static and dynamic level of up to six channels at the same time.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: International Instrumentation Symposium; May 01, 1989 - May 04, 1989; Orlando, FL; United States
    Format: text
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  • 7
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    Force-Balance Dynamic Display (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Balance dynamic display unit (BDDU) is compact system conditioning six dynamic analog signals so they are monitored simultaneously in real time on single-trace oscilloscope. Typical BDDU oscilloscope display in scan mode shows each channel occupying one-sixth of total trace. System features two display modes usable with conventional, single-channel oscilloscope: multiplexed six-channel "bar-graph" format and single-channel display. Two-stage visual and audible limit alarm provided for each channel.
    Keywords: ELECTRONIC SYSTEMS
    Type: LAR-13658 , NASA Tech Briefs (ISSN 0145-319X); 12; 8; P. 32
    Format: text
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  • 8
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    Testing experience with unheated stain-gage balances in the NTF (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A series of cryogenic (cryo) cycles was conducted in the cryo chamber at the National Transonic Facility (NTF) in order to identify the cause of apparent strain shifts in axial force with temperature for the Pathfinder I model and to minimize their effects. The results of the investigation indicated that the major cause of axial force end point shifts and thermal hysteresis loops was the thickness of the Teflon insulation on the instrumentation wires crossing the balance. By reducing the thickness of the insulation and the total number and size of the wires, apparent strain values were achieved for the model with instrumentation wires which were nearly identical to those for the model without wires. Because of the special design features used, the balance output was very accurate and repeatable over the entire NTF temperature range, even with balance thermal gradients as large as 64 F and transient conditions as large as 3 F/minute.
    Keywords: RESEARCH AND SUPPORT FACILITIES (AIR)
    Type: Supersonic Tunnel Association, Semiannual Meeting, 66th, Albuquerque; Oct 06, 1986 - Oct 07, 1986; Albuquerque, NM; United States|; 20 p.
    Format: text
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