Damping of Compression and Shear Piezoelectric Accelerometers By Electromechanical Feedback

Abstract

Piezoelectric (PE) accelerometers exhibit a very pronounced resonance peak in their transfer characteristic of typically 30 dB or more. This high-Q resonance is caused by the very small displacements internally in these devices which are constructed of very stiff seismic masses and ceramic sensing plates. The resonance severely reduces the usefulness of these devices for measurements of vibrations with fast rise-time components which will excite the almost undamped accelerometer resonance, obscuring the real vibration data. Usually, this is solved by limiting the readout amplifier's bandwidth to about one fifth of the resonance frequency, i.e., a large part of the transducer's frequency range is sacrificed to suppress the resonance peak. This paper presents the results of an investigation into applying damping to the accelerometer by electromechanical feedback, using the reversibility of the PE effect. It shows that a maximally flat response (Butterworth) can be obtained with little peaking (approximately 2 dB) and excellent dynamic stability which makes the accelerometer usable up to its resonance frequency. © 1988 IEEE.