Abstract: An improved vibration sensor of a type used to monitor the vibration and knocking level of an automotive engine or the like. The vibration sensor includes a casing having a cavity in which is received a resonant plate composed of a metal plate and a piezoelectric element. The piezoelectric element has electrodes disposed on opposite sides thereof, one abutting the metal plate. The electrode abutting the metal plate has an extended portion which passes around the edge of the piezoelectric body of the piezoelectric element, extending onto the opposite surface with a gap formed between the end of the extended electrode portion and the electrode on this opposite surface. A thin resistor, such as may be formed by a layer of a resistive paste or a chip resistor, is installed across the gap between the end of the extended electrode layer and the opposing electrode.

Abstract: Sheet-like piezoelectric element in which a plurality of slits are formed between the comb-shaped electrodes alternately projected in a zigzag shape from a pair of terminals arranged oppositely, a piezoelectric layer of composite piezoelectric material is filled into the slits, a DC voltage is applied between the terminals to polarize the adjacent layers in reverse directions to each other, and the electrodes have a thickness corresponding to that of the piezoelectric layer. The element may be used for an electro-mechanical transducer or a thermal-electric transducer.