COMPARISON OF METHODS FOR CALIBRATION OF TOTAL AND PARTIAL-PRESSURE GAUGES

For precise measurements of most data required for vacuum system characterization and process control (i.e. gas flow rates, gas amounts and densities, fluences), gauge calibration in terms of pressure is a rather indirect method. A more direct way is to calibrate vacuum systems by means of gas quantities. In this paper two techniques are discussed: the chemical decomposition technique (CDT) and the pressure times volume (P x V) technique, developed and regularly used at Imre Brody Research Center and at Seibersdorf, respectively. Results from an intercomparison of these two methods are given. For CDT, small amounts of CO2 (in the 0.1 mg range) were decomposed under vacuum at about 1000 K. For P x V calibrations, known quantities of CO2 were determined inside a 27 cm3 chamber by the readings of a capacitance diaphragm gauge. The calibration data agree within +/- 5%, possible systematic errors are discussed.