Measurement performance of high-accuracy low-pressure transducers

A systematic study of measurement performance is described for several different types of transducer including capacitance diaphragm gauges (CDGs), quartz Bourdon gauges (QBGs), quartz resonant gauges (QRGs), and two types of MEMS (MicroElectroMechanical Systems) sensors - piezoresistive silicon gauges (PSGs) and resonant silicon gauges (RSGs). Key factors limiting their performance were identified as random noise, short-term instabilities in zero-pressure readings, long-term shifts in a transducer's calibration with time and, in the case of heated gauges, the effect of thermal transpiration. The study determined that CDGs, QBGs, and QRGs have superior noise-limited pressure resolution (about 1 part in 10 6 of full scale), though CDGs, because of their availability with lower full-scale ranges, have the best absolute pressure resolution. Analyses of calibration data indicated that QBGs, QRGs and RSGs have the best long-term stability, with average calibration shifts of the order of 1 part in 10 4 per year, one to two orders of magnitude smaller than those observed for CDGs.