Comparison of two primary pressure standards using spinning rotor gauges

Abstract

In this paper a comparative study of two primary pressure standards viz. static and dynamic gas expander systems is reported. The two systems are compared by using spinning rotor gauges as the transfer standard in the pressure region of 6×10−3 to 2×10−1 Pa. It is observed that if the pressure variation of the conductance of the orifice assembly of the dynamic system is taken into account then the two systems are found to show an agreement of ±0.3% in the overlapping pressure region. A modified mathematical analysis of the equation due to Bureau et al. for molecular conductance of the orifice assembly is also given by taking into account the exit/entrance loss based on the new short-tube transmission probability equation developed by Santeler. The molecular conductance value thus obtained is found to be in close agreement with the corresponding experimental value extrapolated from the conductance versus pressure curve. This modified formula can be used to determine the effective conductance of the orifice assembly irrespective of the position of the orifice inside the tube connecting the two chambers.