Recent advances in vibration and shock measurements and calibrations using laser interferometry

Abstract

In order to establish traceability for vibration and shock measurements, hierarchies of measurement standards have been established and are operated at National Metrology Institutes (NMIs) as well as in accredited and non-accredited calibration laboratories. NMIs make use of laser interferometry, to realize and disseminate the unit and the associated scale of the physical quantity of acceleration. To meet the increasing demands, improved and new standard methods for vibration and shock calibration have been specified and implemented. At the PTB, primary vibration calibration of vibration transducers (accelerometers) by laser interferometry has been extended to the frequency range 0.4 Hz to 20 kHz. This enabled one of the calibration laboratories in Germany, within the framework of the Deutscher Kalibrierdienst (DKD), to be accredited for accelerometer calibration (comparison method) in the wide frequency range of 0.4 Hz to 20 kHz, too. In addition to the magnitude of the complex sensitivity of accelerometers, phases shift calibrations by laser interferometry have been extended to 10 kHz and confirmed by a bi-lateral comparison. Progress in interferometric primary shock calibration (peak acceleration from 50 m/s2 to 100 km/s2) has made it possible to perform accelerometer linearity tests of low uncertainty better than 1%. High-accuracy calibrations of laser vibrometers have been achieved at frequencies up to 20 kHz. A novel high-frequency vibration exciter proved to be the basis for extending the calibration capabilities for laser interferometers towards higher frequencies (current target at PTB: 60 kHz). The advances achieved are described and demonstrated by experimental results.

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