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Technical Information
Gas Correction Factors
Table 2 lists the relative gauge gas correction factors for various gases.
WARNING
Do not assume that the use of the gases listed in this table are safe
with hot filament gauge controllers.
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):
Pls refer to XGS instruction manual for gas correction setting.
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.
Some gases have several correction factors listed. In such cases, the top number is
NOTE
the most commonly-used value.
26
Agilent UHV-24/UHV-24p Ionization Gauge User Manual
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