GB180787A - - Google Patents

Abstract

180,787. Wood, A. B. March 15, 1921. Indicating, optical devices for.-An electrostatic oscillograph or voltmeter comprises a piezo-electric crystal slice with means for applying a direct or alternating current potential in the direction of the electric axis of the slice, he dilation or contraction produced being determined by means giving measurable indications of the deformation. As shown, the piezoelectric crystal slice A is fixed at one end B and is positioned between two strips of tin-foil F making contact with spring arms G, to which the potential is applied. The free end of the slice is formed with a knife-edge D which cooperates with a fixed knife-edge E, a light mirror H being elastically cemented, for example, by soft rubber to both knife edges, or held against the knife-edges by a spring, so that the mirror is rocked through a small angle as the slice dilates and contracts. In another construction, two piezo-electric crystal slices are mounted together in opposite senses so that a greater movement is imparted to the mirror which in this construction is, in its normal position, parallel to the surfaces of the slices.