Hans Hellebrand

Optical two channel elongation measurement of PZT piezoelectric multilayer stack actuators

A fast optical deflection measurement of multilayer actuators is described. This two beam method eliminates the measuring problems arising from fixing one side of clamped actuators by detecting the movements of both sides of the actuator. The frequency range of this interferometric measurement reaches from static up to 200 kHz. In this way fast mechanical response can be detected even in the case of rectangular pulses. The accuracy of the deflection measurement is better than 1%. The small and large signal effective d/sub 33/ data of PZT multilayer actuators, consisting of up to 500 single layers, are determined using this method. The dependence of these data on clamping force and pulse duration is investigated. For characterization of reliability of multilayer actuators the maximum number of cycles under hard driving conditions of rectangular pulses with rise times of 10 /spl mu/s leading to maximum loading currents of 20 A is determined.