Ionization gauge and method of using and calibrating same

Details Ionization gauge and method of using and calibrating same Ionization gauge and method of using and calibrating same

1996-11-12

1998-09-01

Raevis, Robert

Electricity: measuring and testing

Using ionization effects

For monitoring pressure

G01L 2132

Patent

active

058015353

ABSTRACT:
Controller circuitry and method for controlling the operation of an ionization gauge having a source of electrons, an anode, an ion collector electrode. Circuitry is provided (a) for providing an electron emission current from the electron source (b) for measuring the heating power W.sub.X of the electron source to obtain a measured value of the heating power at an unknown pressure P.sub.X and (c) measuring the ion current to the collector electrode to obtain a measured value of the positive ion current i.sub.+X at the unknown pressure. A memory is also provided for storing at least one equation for pressure, the pressure equation being obtained from a reference gauge by measuring the current i.sub.+cal to the positive ion collector electrode, the electron emission current i.sub.-cal from the electron source and the heating power W.sub.cal of the electron source of the reference gauge at selected calibration pressures P.sub.cal and selected heating powers W.sub.cal of the electron source of the reference gauge, the equation for pressure being in the form of P=f(i.sub.+ /i.sub.-, W). Moreover, a calculator responsive to the stored equation for pressure and the measured values of positive ion collector current i.sub.+X and heating power W.sub.X of the electron source is provided for calculating a pressure indication P.sub.XI when the predetermined pressure gauge is exposed to the unknown pressure P.sub.X at an emission current i.sub.-cal of the electron source, the pressure indication being calculated according to the equation P.sub.XI =f (i.sub.+X /i.sub.-cal, W.sub.X). Means are also provided such that, for a given pressure of the gas and cathode temperature, the temperature of the internal surfaces of the gauge will be substantially repeatable over time and reproducible gauge to gauge.

REFERENCES:
patent: 4468968 (1984-09-01), Kee
patent: 4866640 (1989-09-01), Morrison, Jr.
patent: 5128617 (1992-07-01), Bills
patent: 5250906 (1993-10-01), Bills et al.
patent: 5296817 (1994-03-01), Bills et al.
patent: 5422573 (1995-06-01), Bills et al.

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