Emerson NGA 2000 TO2 - Manual (Page 38)

Instruction Manual
760008-A
September 2001
3-14 Operation Rosemount Analytical Inc. A Division of Emerson Process Management
Model NGA 2000 TO2
a. Calibration Procedure
The TO2 analyzer module is fully factory
calibrated prior to shipment using certified
gas standards. If the analyzer is operated
within its specified operating conditions,
no regular calibration is required. The
zero calibration is very stable and does
not require checking more than once a
year.
Gas Scale Factor
The Gas Scale Factor is used to correct
for background gases other than nitrogen.
When the background of the sample is
other than nitrogen, the diffusion rate of
oxygen into the sensor changes. By cor-
recting for the background difference, the
diffusion change can be compensated in
software. The GSF can be entered manu-
ally or calculated automatically. Calcula-
tion of the GSF requires the user to enter
the sample gas composition. In most ap-
plications, the GSF is not required. How-
ever, some backgrounds exhibit
significantly different diffusion character-
istics versus nitrogen (such as helium or
hydrogen) and the GSF may improve
performance.
Set the Gas Scale Factor as follows: