Appendix C. Gas Correction Factor Table - Varian XGS-600 Instruction Manual

Appendix C. Gas Correction Factor Table

Table C-1 on page C-2 lists relative gauge gas correction factors for various gases. The table
is reproduced for convenience only.
The values are derived by empirical methods substantiated by measurements reported in
literature. This table was compiled and published by Robert L. Summers of Lewis Research
Center, NASA Technical Note TND-5285, National Aeronautics and Space Administration,
Washington, DC, June 1969.
To automatically convert readings of the XGS-600 Controller, normally calibrated for
nitrogen, to read pressures of the other gasses:
1. Use Sensor Setup to access the GAS CORRECTION function.
2. Enter the relative gas correction constant.
The gauge divides the result by the gas correction constant and displays the correct
adjusted value. The default for Gas Correction is 1.
The correction for different gas species is purely arithmetic. The sensitivity of the tube is
affected by different gases which, in turn, are responsible for the tube output being
manipulated by the pressure equation. There is some loss in resolution of the instrument
when gas correction constants are used. The loss in resolution becomes more apparent as
the correction constants approach 0.5 from either direction.
When the correction constants are 0.1 or 10, the tube output is 1/10 or 10 times normal.
This causes the instrument to lose the high vacuum decade or the near atmosphere decade,
respectively.
XGS-600 Gauge Controller
WARNING
The XGS-6000 used with any ion or convection gauge is NOT
considered intrinsically safe, and should not be used with potentially
flammable or explosive gas mixtures.
C-1