USE OF CAPACITANCE DIAPHRAGM GAUGES AT PRESSURES DOWN TO 10(-6) TORR

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.