Development and Characterization of Volume Expansion Vacuum Standard

A multi-stage primary vacuum standard system for the generation of calibration pressures, in the range 10 -10 mbar has been developed. It is based on volume expansion method, whereby the range is 0 4 extended to lower pressures by multiple expansions. The standard system consists of four chambers that help to achieve a pressure reduction by a factor of about 10 in the main calibration chamber after a four-step 5 expansion. The entire system is built using ultrahigh vacuum techniques. For performance characterization, results have been compared with that of a secondary standard i.e. Capacitance Diaphragm Gauge (CDG). The average value of correction factor is 0.995 while linear correlation coefficient of primary–secondary standard is found to be 1.00. Various uncertainties of the generated pressures by this method have been calculated. The combined uncertainties lie between 1.73×10 mbar and 9.18×10 mbar. The values of relative uncertainty are 3 6 found to be in the range 10 10 . The standard system is cost effective and simple in construction, compact 2 3 and user friendly with high precision.