Mechanical Measurements

Vibration Measurements

Technical Contacts:
David J. Evans
Tel: 301/975-6637
E-mail: david.evans@nist.gov

Kari Harper
Tel: 301/975-6612
E-mail: kari.harper@nist.gov

Toni Savoy
Tel: 301/975-6613
E-mail: toni.savoy@nist.gov

Administrative and Logistics:
Michelle Masser
Tel: 301/975-3506
Fax: 301/975-8058
E-mail: michelle.masser@nist.gov

Do not ship instruments or standards to the mailing address listed below. Contact the technical staff for the shipping address. 

Mailing Address:
National Institute of Standards and Technology
100 Bureau Drive, Stop 8220
Gaithersburg, MD 20899-8220

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Transducer Sensitivity (24010C-24030C)

NIST calibrations of vibration exciters and pickups are performed by comparison with the response characteristics of NIST standards or by absolute measurements. A calibration consists of measuring the transfer function of the instrument, usually referred to as the sensitivity. For a pickup, it is the ratio of the electrical output to a mechanical input. The magnitude of the latter is set in accordance with the calibration method, the type of vibration exciter, and the frequency of vibration. The magnitude of the output depends, of course, on the nature of the test device. In the case of an accelerometer with signal conditioner, the practice has been to express the output in millivolts, and the input in units of gn, the standard acceleration of free fall:

g _n = 9.80665 ms^-2

The acceleration sensitivity is then given in mV/g _n. For charge-output devices without signal conditioners, the acceleration sensitivity is stated in picocoulombs per g _n (pC/g _n). All measurements are performed at 23 ± 3 °C. The calibration of an accelerometer is reported in tabular form as the sensitivity magnitude at a set of discrete frequencies; the phase component can be furnished at additional cost on request. The NIST vibration standards are periodically calibrated by reciprocity and/or interferometric techniques, two independent and absolute methods. The use of these standards in the calibration of stable transducers furnishes calibration data with a typical relative expanded uncertainty of 1 % to 2 % depending on the frequency range.

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Special Shock Measurement Services (24040S)

The shock facility provides a comparison calibration of accelerometers by subjecting them to half-sinewave pulses with peak amplitudes of 20 g _n to 10 000 g _n and pulse widths from 0.1 ms to 40 ms. Both time and frequency domain measurements can be performed.

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Special Tests of Transducer Sensitivity (24050S)

This test measures the pickup sensitivity by the fringe-disappearance method, using an automated Michelson interferometer. As presently configured, the system operates between 3 kHz and 20 kHz. The method requires precise setting of vibration amplitude to 121.10 nm; consequently, the acceleration amplitude in the stated frequency range increases from about 4 g _n to 200 g _n.

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Special Vibration Tests (24060S)

Calibration of vibration and shock-measuring instruments to specifications other than those above, as well as other specified measurements, can be performed by prearrangement.

For example, an interferometer calibration for frequencies less than 2 Hz or greater than 10 kHz can be performed on request. Consult with the technical contacts cited at the beginning of this section.

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References-Vibration Measurements

An Application of Parameter Estimation Theory in Low Frequency Accelerometers , B. F. Payne and M. R. Serbyn, 14th Transducer Workshop, Telemetry Group, Range Commanders Council, Colorado Springs, CO (June 1987).

A Description of NBS Calibration Services in Mechanical Vibration and Shock, D. C. Robinson, M. R. Serbyn, and B. F. Payne, Natl. Bur. Stand. (U.S.), Tech. Note 1232 (Feb. 1987).

An Automated Fringe Counting Laser Interferometer for Low Frequency Vibration Measurements , B. F. Payne and C. Federman, Proc. ISA Symp., Seattle, WA (May 1986).

Automation of Vibration Testing at the National Bureau of Standards , B. F. Payne, Proc. 30th Tech. Meeting, Inst. of Environ. Sciences (May 1984).

An Automated System for the Absolute Measurement of Pickup Sensitivity , B. F. Payne and M. R. Serbyn, Proc. Natl. Conf. Stand. Lab. Ann. Workshop and Symp. II-11.1-II-11.22 (July 1983).

The Application of Back-to-Back Accelerometers to Precision Vibration Measurements, B. F. Payne, J. Res. Natl. Bur. Stand. (U.S.) 88 (3), 171 (May-June 1983).

A Real-Time Active Vibration Controller , M. R. Serbyn and W. B. Penzes, ISA Transactions 21 (3), 55 (1982).

Development of a Low-Frequency-Vibration Calibration System, R. S. Koyanagi, Exp. Mech. 15, 443 (Nov. 1975).

Shock Calibration of Accelerometers, C. Federman, W. Walston, and J. Ramboz, Minutes of the 8th Transducer Workshop: Telemetry Group, Inter-Range Instrumentation Group, Range Commanders Council, Wright-Patterson AFB, OH (Apr. 1975).

Piezoelectric Shakers for Wide Frequency Calibration of Vibration Pick-ups, E. Jones, B. Yelon, and S. Edelman, J. Acoust. Soc. Am. 46 (6), 1556 (June 1969).

Improved Transfer Standard for Vibration Pickups , E. Jones, D. Lee, and S. Edelman, J. Acoust. Soc. Am. 41 (2), 354 (Feb. 1967).

Electrodynamic Vibration Standard with a Ceramic Moving Element , T. Dimoff, J. Acoust. Soc. Am. 40 (3), 671 (Sept. 1966).

Calibration of Vibration Pickups at Large Amplitudes , E. Jones, S. Edelman, and K. S. Sizemore, J. Acoust. Soc. Am. 33 (11), 1462 (Nov. 1961).

Calibration of Vibration Pickups by the Reciprocity Method, S. Levy and R. R. Bouche, J. Res. Natl. Bur. Stand. (U.S.) 57 (4), 227 (Oct. 1956).

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