Quartz-Crystal Clock

an instrument for exact time measurements. Its operation depends on the oscillations of a quartz-crystal oscillator. The accuracy of the time readings is determined by the stability of the oscillation frequency of the oscillator and by its quality factor. Since the frequency v of a precision quartz-crystal resonator depends on temperature (Δv/v≦ 10^-8 per degree C), the resonator is placed in a temperature-controlled enclosure with an accuracy of 0.001°C.

In addition to a quartz-crystal oscillator, a quartz-crystal clock also contains oscillation frequency converters (dividers and multipliers); a synchronous motor that drives the clock hands (or a digital counter); and a contact device for the transmission of exact time signals. Quartz-crystal clocks are usually equipped with devices that emit a set of standard frequencies for purposes of measurement. For exact time service two or three quartz-crystal clocks are used simultaneously; their frequencies are compared with each other, with a quantum frequency standard, and with data derived from astronomical observations.