Ionization gauge and method of using and calibrating same

Abstract

Controller circuitry and method for controlling the operation of an ionization gauge having a source of electrons, an anode, and an ion collector electrode, including storing a plurality of calibration data sets for at least collector electrode currents and gauge sensitivities obtained with at least one reference gauge at representative values of known pressures; and calculating the gauge sensitivity corresponding to an unknown pressure in response to at least one of the data sets together with a measured value of the ion collector current. The data sets may also include representative values of the heating powers of the electron source so that the calculated sensitivity may also be compensated for variations in the electron source heating power. The ionization gauge may be of the Bayard-Alpert type and include a shield which defines a shielded volume within which an electron source, anode, and collector electrode are disposed where the shield is at least partially open to permit transfer of gas molecules into the shielded volume and where the shield completely encloses the electron source, the anode and the collector electrode so that potentials external to the shield means do not disturb the electric charge distribution within the shielded volume to thus stabilize the sensitivity of the gauge.