Design and performance of a quartz oscillator vacuum gauge with a controller

We designed, built, and tested the first model of a quartz friction vacuum gauge and its controller, using a tuning fork shaped miniature quartz oscillator of a wristwatch as a pressure sensor. This gauge made it possible to measure pressure from 0.01 Torr to more than 760 Torr with an accuracy of better than 10%. The oscillator was installed on a small‐sized vacuum flange and driven at its resonance frequency by constant amplitude ac voltage fed by a phase‐locked loop oscillation circuit. The resonance current of the oscillator was rectified and amplified to actuate a meter and/or a recorder. The pressure dependence of the readings of the gauge for various gases was measured, and found to be in agreement with theoretical predictions. The performance of the gauge was unaffected by hundreds of repetitions of a quick evacuation from atmospheric pressure to less than 0.001 Torr and an exposure to the air.