Sinusoidal vibration measurements using optimal measurement intervals

Highly accurate vibration measurements and primary calibrations using laser interferometry require measurement signals with a high signal-to-noise ratio. Low-frequency disturbances in particular can strongly affect the measurement accuracy. The methods frequently used for the suppression of low-frequency disturbances such as digital filters or window functions require relatively long measurement times to ensure sufficient suppression. For the measurement of low-frequency vibrations and real-time measurement tasks, such sufficiently long time intervals are scarcely possible. This paper is focussed on short-time vibration measurements. It presents an analysis of the so-called sine-approximation method (SAM) which is widely used in vibration (calibration) measurements. The results presented are related to a third-order model and an extended model (fourth order) for fitting to the measurement data a sinusoidal signal on which a linear time-dependent drift is superimposed. For both models different optimal measurement intervals could be determined realizing a high suppression of low-frequency disturbing signals in estimating amplitude and phase of the vibration signal. The simulation results are verified by analysis of real data obtained with a high-frequency acceleration standard device. (C) 2003 Published by Elsevier Ltd.