Reproducibility of the performance of Pirani gauges

Abstract

A study has been made of the reproducibility of the calibration of a number of Pirani gauges operating in both the constant temperature and constant voltage modes under clean vacuum conditions within the pressure range 10−3 to 10 Torr (0.133 to 1.33×103 Pa). The calibrations were performed using nitrogen and argon at various times during a six-month period. It was found that the constant temperature version was reproducible to within±6% over the pressure range 10−2 to 10 Torr (1.33 to 1.33×103 Pa) and the constant voltage version had a similar reproducibility over the range 10−3 to 1.0 Torr (0.133 to 133 Pa). This study included measurements to investigate the effects of storage conditions and temperature on the calibration of the gauges, and by generating the pressures in a rising and falling sequence it was also possible to check for any hysteresis effects. It is concluded that these gauges, when used under well defined conditions, may be used as reference gauges for the routine checking of other gauges of this type used on industrial vacuum systems.