Gas and Mode, Vertical and Rotational Effects with a Three Piston Gauge Apparatus

A semi-automated three piston gauge apparatus has been used to measure gas species and mode effects in a low pressure pneumatic dead-weight piston gauge. Two gases, He and N2, were used in both gauge and absolute modes, as well as several "intermediate" modes, to characterize a single gauge. The results of the measurements are compared with a model for crevice effects that incorporates both molecular and viscous flow regimes. The model has previously been applied to spin decay rate measurements on the four gases He, N2, H2 and SF6, and has now been extended to account for differences in effective area arising from species changes. Mode effects remain that cannot be predicted by the model.