GB1286987A - A method of compensating the pyroelectric effect in electromechanical transducers, particularly in ferroelectrics, and an arrangement for performing the same - Google Patents

Abstract

1286987 Piezo-electric elements METRAMESSUND FREQUENZTECHNIK RICHARD WEBER KG 4 Oct 1969 48853/69 Heading H1E The pyro-electric effect in electromechanical transducers employing the longitudinal, transverse, or shear, piezo-electric effect is compensated by the use of two pairs of electrodes, the pairs being of such relative disposition and area, and so interconnected, as to ensure the mutual cancellation of the changes of surface charge arising at the electrodes due to the pyro-electric effect upon a change of temperature. In the arrangement of Fig. 4, the electrode areas or pyro-electric coefficients of the two plates 6 and 7 are chosen such that, when connected as shown, cancellation of the pyroelectric surface charges occurs, the mechanical force for application to the transducer being arranged to apply tensile stress to one plate and compressive stress to the other, in order to prevent cancellation of the signal which results from mechanical strain. For the shear loaded piezo-electric element of Fig. 6, pyro-electric charges appearing at the principal electrodes 4 and 5 due to the polarization vector not being strictly parallel to those faces are compensated by the pair of electrodes 8 and 9 (electrode 8, only, appears inFig. 6) which are connected to the principal electrodes. The arrangement facilitates the use as transducers of ceramic ferro-electric materials, which are pyre-electric.