Operation
Calibration Factors Menu
3-16
Model 43i Trace Level-Enhanced Instruction Manual
Thermo Fisher Scientific
The SO
2
Background correction is determined during zero calibration. The
SO
2
background is the amount of signal read by the analyzer while
sampling zero air. Although the background is expressed in terms of
concentration, the background signal is actually the combination of
electrical noise and scattered light. Before the analyzer sets the SO
2
reading
to zero, it stores this value as the SO
2
background correction.
The SO
2
Background screen is used to perform a manual adjustment of the
instruments zero background. As such, the instrument should sample zero
air until stable readings are obtained. The display shows the current SO
2
reading. This reading is the SO
2
background signal. The next line of the
display shows the SO
2
background correction that is stored in memory and
is being used to correct the SO
2
reading. That is, the SO
2
background
correction is subtracted from the SO
2
reading.
In the example that follows, the analyzer is reading 1.49 ppb of SO
2
while
sampling zero air. The SO
2
background correction is 0.0 ppb. 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 1.49 ppb in order for the SO
2
reading to be at 0 ppb.
To set the SO
2
reading in the example that follows to zero, use
to
increment the SO
2
background correction to 1.49 ppb. As the SO
2
background correction is increased, the SO
2
concentration is decreased. At
this point, however, no real changes have been made. To escape this screen
without saving any changes, press
to return to the Calibration
Factors menu or
to return to the Run screen. Press
to actually
set the SO
2
reading to 0 ppb and store the new background correction of
1.49 ppb.
In the Main Menu, choose Calibration Factors
> SO
2
Bkg
.
SO
2
Background
CALIBRATION FACTORS:
>SO2 BKG 0.00
SO2 COEF 1.000
RESET USER CAL DEFAULTS
RANGE AVG DIAGS ALARM
CALIBRATION FACTORS:
>SO2 BKG 1.49
HI SO2 COEF 1.000
LO SO2 COEF 1.000
RESET USER CAL DEFAULTS
RANGE AVG DIAGS ALARM
