Abstract: A piezoelectric sensor system according to the invention employs a piezoelectric actuator relay (20) having a piezoelectric element displaceable in response to an actuation voltage and contacts (23, 24) which open or close in accordance with the displacement of the element, wherein the actuator relay (20) is adapted to receive a force (L) to be measured against the displacement. This piezoelectric actuator relay (20) is supplied, by a driver circuit (60), with a varying voltage as the actuation voltage. The relation between the forces (L) and the activation voltages necessary for opening or closing the contacts (23, 24) has been stored in a memory (70). A processor (50) obtains a value of the force (L) based on a value of the actuation voltage at the instant of the opening or closure of the contacts (23, 24) and the relation stored in the memory (70).

Abstract: A piezoelectric actuator, which has a large displacement rate and a relatively simple structure, is capable of providing an output without the need for a specific support and can be manufactured at low costs, is provided. The piezoelectric actuator 10 takes a planar plate-like form and has first and second layer regions 11 and 12 lying one upon the other. The first layer region 11 is formed comprising a piezoelectric ceramic material and contains electrodes 13-1 to 13-n for receiving an actuation voltage to cause this first layer region to contract in a plane parallel thereto. The second layer region 12 is formed integrally with the first layer region 11 and comprises a ceramic material.