Piezo-Electric Terminology

The following familiar terms are first recapitulated: direct and converse piezo-electric effects, longitudinal and transverse effects, longitudinal, transverse, flexural, and torsional vibrations. It is suggested that when the bending of a bar or plate is involved, the term "flexural" rather than "transverse" be adopted. With reference to quartz crystals, the terms "X-cut" and "Y-cut" are recommended in place of "Curie cut" and "thirty-degree cut" for plates perpendicular tothe X and Y axes respectively. It is suggested that the terms "X-waves," "Y-waves", or "Z-waves" be applied to waves of mechanical vibration the direction of propagation of which is parallel to the X, Y, or Z axis respectively, whatever the mode of vibration. For the quantity "meters per millimeter," the name wave-constant, to be designated by the symbol h, is recommended. Brief mention is made of the simpler types of vibration of Rochelle salt plates. A piezo-electric resonator is defined as any device that may be excited piezo-electrically into resonant vibration at one or more frequencies. In a more restricted sense the term is also applied to such a device when so connected as to exert no appreciable controlling effect upon the applied frequency through its reaction. A piezo-electric stabilizer controls over a narrow range the freqquency of a circuit which already oscillates, while a piezo-electric oscillator controls the frequency of an oscillating circuit which in the absence of the crystal would not oscillate. The same crystal may of course function in any one of the three ways, depending upon circuit conditions.