On the calibration of laser Doppler vibrometers using simulated excitation

This contribution shares some points probably not so commonly aware in the community of acceleration calibration that we have investigated to build up a new laser Doppler vibrometer (LDV) calibration facility using simulated excitation in our lab at PTB. The simulated excitation of LDVs offers opportunities to extend the frequency and amplitude calibration range without the need of elaborated mechanics while reducing measurement uncertainties by mainly working with electrical and time/frequency quantities. Two different stimulation methods are outlined: The optical stimulation with an amplitude-modulated laser diode, exciting the photo diode of the LDV interferometer, and the electrical stimulation as a replacement of the LDV interferometer where applicable. Phase noise of the involved oscillators and sample clocks results in higher noise levels and uncertainties in heterodyne measurements. Methods for synchronisation and the effect on the measurement uncertainty are presented.