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CO Background
Thermo Fisher Scientific
The CO background correction is determined during zero calibration. The
CO background is the amount of signal read by the analyzer while
sampling zero air. The background signal is electrical noise. Before the
analyzer sets the CO reading to zero, it stores this value as the CO
background correction.
The CO Background screen is used to perform a manual zero calibration of
the instrument. As such, the instrument should sample zero air until stable
readings are obtained. The first line of the display shows the current CO
reading. This reading is the CO background signal. The second line of the
display shows the CO background correction that is stored in memory and
is being used to correct the CO reading. That is, the CO background
correction is subtracted from the CO reading.
In the example below, the analyzer is reading 1.4 ppm of CO while
sampling zero air. The CO background correction is 0.0 ppm. That is, the
analyzer is not applying a zero background correction. The question mark
is used as a prompt to change the background correction. In this case the
background correction must be increased to 1.4 ppm in order for the CO
reading to be at 0 ppm.
To set the CO reading in the example below to zero, use
increment the CO background correction to 1.4 ppm. As the CO
background correction is increased, the CO concentration is decreased. At
this point, however, no real changes have been made. To escape this screen
without making any changes, press
Factors menu or
set the CO reading to 0 ppm and store the background correction of 1.4
ppm.
In the Main Menu, choose Calibration Factors > Bkg.
●
CO BACKGROUND:
CO:
SET BKG TO:
RANGE
AVG
to return to the Calibration
to return to the Run screen. Press
1.4
0.0
INC/DEC
SAVE VALUE
DIAGS ALARM
Model 48i Trace Level-Enhanced Instruction Manual
Operation
Calibration Factors Menu
to
to actually
3-17
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