Gauge calibration

Abstract

There are three alternative techniques available for Use in industrial and research laboratories where the calibrations can be carried out (i) by comparison with a ‘transferable’ or ‘reference’ gauge which is subject to periodic calibration in a National Standard or equivalent laboratory; (ii) against a fundamental standard which may be a true pressure (for example a McLeod) gauge; (iii) on a plant especially designed to produce precise pressures. Due to the extensive developments in the design and construction of the reference gauges (the capacitance manometer, section 1.3, and the spinning rotor gauge, section 1.4) it is the former technique which has the greatest attraction for most vacuum workers. With the comparison techniques, calibration of practical working gauges, such as the ionization and thermal conductivity, can be made down to pressures of 10⁻⁴ mbar, with uncertainties of the order of ± 5%. It requires a considerable investment in both skill and finance to obtain a significant improvement in this performance.