Calibration of vibration pickups at high frequencies

Improved design of vibration pickups by several accelerometer manufacturers has results in low-mass or miniature accelerometers with extended frequency response. This paper discusses methods for measuring the frequency response (calibration) of this type of miniature accelerometer. By using a calibration system composed of a Michelson interferometer with a helium-neon laser as a light source, absolute displacement measurements can be obtained over the frequency range of approximately 2 to 30 kHz. Using techniques developed at NBS, measurements can be obtained at amplitudes of 121 nm and 193 nm. Since the vibration exciters have limitations in amplitude, the 121-nm technique enables higher frequency measurement capability. These measurement techniques and the experimental measurement apparatus are discussed in this paper. An example of a measurement on a miniature accelerometer over the frequency range of 10 Hz to 30 Hz is discussed.