A New Quartz-Crystal Plate, Designated the GT, Which Produces a Very Constant Frequency over a Wide Temperature Range

In this paper, a new quartz-crystal plate, designated the GT, is described which produces a very constant frequency over a wide temperature range. This crystal does not change by more than one part in a million over a 100-degree centigrade range of temperature. This crystal obtains its great temperature stability from the fact that both the first and second derivatives of the frequency by the temperature are zero. Both the frequency and temperature coefficient can be independently adjusted. This crystal has been applied in frequency standards, in very precise oscillators, and in filters subject to large temperature variations. It has given a constancy of frequency considerably in excess of that obtained by any other crystal. A crystal chronometer, using this type of crystal, was recently lent to the Geophysical Union for measurements on the variation of gravity and the chronometer is reported to have kept time within several parts in 10 million, although no temperature control was used.