Appendix A. Gas Correction Factor Table - Agilent Technologies UHV-24 Instruction Manual

Appendix A. Gas Correction Factor Table

Table 2 on page 20 lists the relative gauge gas correction factors for various gases.
The values in Table 2 are derived by empirical methods substantiated by measurements
reported in literature. This table has been 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 the UHV-24/UHV-24p readings (normally calibrated for nitrogen):
❑
Enter the relative gas correction constant through the front panel key function F GAS
CORR.
When the gas constant is entered, the gauge divides the result by the gas correction
constant and displays the correct adjusted value.
A proper understanding for the transformation of the result is still, however, required.
The correction for different gas species is purely mathematical. The tube sensitivity tube
is affected by different gases which, in turn, is responsible for the tube output being
manipulated by the pressure equation. In addition, There is 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.
UHV-24/UHV-24p Ionization Gauge
WARNING
Do not assume that the use of the gases listed in this table are
safe with hot filament gauge controllers.
NOTE
Some gases have several correction factors listed. In such cases,
the top number is the most commonly-used value.
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