Use of capacitance diaphragm gauges at pressures down to 10^-6 Torr

H. C. Straub, P. Renault, B. G. Lindsay, K. A. Smith and R. F. Stebbings

Rev. Sci. Inst. 65, 3279-3281 (1994)

The useful range of a capacitance diaphragm gauge is extended down to 1 X 10^-6 Torr with an uncertainty of ±10^-7 Torr using computer-based averaging. Gauge linearity is measured by observing the deflection of the diaphragm by the force of gravity. Precise pressure increments are generated by tilting the gauge through a range of accurately measured angles. By this procedure the gauge is observed to be linear to within ±1% plus 10^-7 Torr between 1 X 10^-6 and 8 X 10^-3 Torr. Additionally, the deflection of the center of the diaphragm per unit pressure is found to be 2 X 10^-5 m Torr^-1.