MEASUREMENTS OF TEMPERATURE COEFFICIENT AND PRESSURE COEFFICIENT OF QUARTZ CRYSTAL OSCILLATORS
S. Leroy Brown, Sidon Harris · Review of Scientific Instruments · 1931
A method of measurement is used whereby variation in frequency of a high frequency oscillator can be measured easily to a fraction of a part in a million. The audible difference tone produced by a harmonic of a constant, high frequency oscillator and a harmonic of a second oscillator is compared to the tone of a variable, calibrated audio frequency oscillator. Any change of the frequency of the second high frequency oscillator is measured to a fraction of a cycle per second. This method of measurement is used to determine the effects of temperature and pressure on the frequency of a piezo-electric oscillator. The temperature effect is of the order of 20 parts per million per degree centigrade while the pressure effect is of the order of only 6 parts per million per atmosphere.