Gauge calibration in the high and medium vacuum range by a series expansion standard

Abstract

Among the various types of calibration standards, the series expansion scheme provides the highest accuracy in the high and medium vacuum range. In this method the generated calibration pressure is obtained from the initial pressure (in the low vacuum range) and the pressure reduction factor. Disturbances arise by the nonideal gas behaviour, temperature effects and gas adsorption at the walls. The performance of the new PTB series expansion apparatus is investigated in detail; emphasis is laid on the exploration of the disturbances. The uncertainty of the generated pressure is mainly limited by uncertainties of the pressure reduction factors, i.e. the ratios of vessel volumes and its 1σ-values are 0.05% at 10 mbar and 0.2% at 10 −6 mbar.