5. Pressure gauges and instrumentation

Vacuum covers pressures up to atmospheric pressure. Pressure gauges used in the pressure range can perfectly well also be used in the coarse to medium vacuum range. Resonant pressure gauges (those that specifically measure absolute pressure) are presented in this chapter. These are based on a mechanical principle. Capacitive diaphragm pressure gauges (when used as absolute pressure gauges) are widely regarded as vacuum gauges, although their principle is based on mechanical deformation. Ultimately, under high vacuum (table 1 ), such manometers can detect a pressure variation of the order of 1 × 10 ^–4 Pa. The metrological performance of manometers based on mechanical principles is interesting above around 1 Pascal....