Thermo Scientific 42i Instruction Manual page 56

Operation
Calibration Factors Menu
3-18 Model 42i Instruction Manual
and NO background corrections and is not displayed. The background
x
corrections are typically below 15 ppb.
The NO and NO Background screens are used to perform a manual zero
x
calibration of the instrument. Before performing a manual zero adjustment,
allow the analyzer to sample zero air until stable readings are obtained. The
NO channel should be calibrated first. Both the NO and NO
screens operate the same way. Therefore, the following description of the
NO background applies to the NO
line of the display shows the current NO reading. The second line of the
display shows the NO background correction that is stored in memory.
The NO background correction is a value, expressed in the current gas
units, that is subtracted from the NO reading to produce the NO reading
that is displayed.
In the example below, the analyzer is displayed 4.4 ppb of NO while
sampling zero air. A background correction is 0.0 ppb means that 0 ppb is
being subtracted from the NO concentration being displayed. Therefore,
the background correction must be increased to 4.4 ppb in order for the
NO reading to be at 0 ppb, that is, a NO reading of 4.4 ppb minus a NO
background reading of 4.4 ppb gives the corrected NO reading of 0 ppb.
To set the NO reading in the following example to zero, use
increment the NO background correction to 4.4 ppb. As the NO
background correction is increased, the NO concentration is decreased.
Note that at this point, pressing
analog outputs or the stored NO background correction of 0.0 ppb. A
question mark following both the NO reading and the NO background
correction indicates that these are proposed changes as opposed to
implemented changes. To escape this screen without saving any changes,
press to return to the Calibration Factors menu or
to the Run screen. Press
store the new background correction of 4.4 ppb. Then the question mark
prompt beside the NO reading disappears.
In the Main Menu, choose Calibration Factors > NO or NOx Bkg.
●
NO BACKGROUND:
NO:
SET BKG TO:
RANGE AVG
background screen as well. The first
x
and
to actually set the NO reading to 0 ppb and
4.4
0.00 ?
 INC/DEC

SAVE VALUE
DIAGS ALARM
Background
x
to
has no affect on the
to return
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