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 deflecti
on of the diaphragm by the force of gravity. Precise pressure incremen
ts are generated by tilting the gauge through a range of accurately me
asured 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.