An Orifice System for Vacuum Gauge Calibration (1)

An orifice system capable of producting the steady-state conditions of known pressures from 10-3 to 10-6 Torr has been made for the practical calibration of vacuum gauges. In such a system, the pressures can be theoretically estimated from the geometrical dimensions of the orifice system and the throughput of the gas introduced into the test dome. The conductance of the orifice was calculated according to Eq. 8, proposed by Bureau, Laslett, and Keller.It has been ensured that the calibration factors of an identical gauge obtained by changing the orifices of different diameters are in fair agreement. However, the estimated pressures in this system seem slightly to differ from the values observed with a sub-standard ionization gauge, the ratio being of 1.08. The discrepancy may be due to the conductance estimation of the orifice system.