Quartz Crystal Thermometer for Measuring Temperature Deviations in the 10−3 to 10−6 °C Range

Abstract

Measurement of temperature deviations in the 10⁻³ to 10⁻⁶°C range has been made, using a specially designed 5‐Mc quartz crystal unit. The crystal unit consists of a 5° Y‐cut crystal plate in a glass bulb. The oscillator is a Pierce‐type transistor circuit similar to those presently in use in ground station frequency standards. The crystal units have a temperature‐frequency coefficient of approximately 80 parts per 10⁶/°C. The crystal Q is of the order of 3 million, and the oscillator has a short time stability of 3 pp 10¹⁰, giving a temperature sensitivity of 3.8×10⁻⁶°C for periods of the order of 10 sec. To measure temperature deviations of a few microdegrees requires the ability to measure frequency deviations of a few parts in 10¹⁰. However, to measure temperature deviations of a few tenths of a millidegree, it is necessary only to measure frequency deviations of a few parts in 10⁸.