Calibration
Zero and Span Check
4-20
Model 42
i
Trace Level Instruction Manual
Thermo Fisher Scientific
Use the following procedure to calibrate the NO
2
channel to the NO
2
calibration gas.
1.
Adjust the O
3
generator in the GPT system to generate sufficient O
3
to
produce a decrease in the high NO concentration equivalent to about
80% of the URL of the high NO
2
range. The decrease must not exceed
90% of the high NO concentration determined in the “Calibrate High
NO
x
” procedure.
2.
From the Main Menu, choose Calibration >
Cal Hi NO2 Coefficient
.
The Hi NO
2
field displays the current NO
2
concentration. The Hi
NO
2
Span Conc field is where you enter the high NO
2
calibration gas
concentration.
3.
Set the high NO
2
calibration gas concentration to reflect the sum of the
NO
2
concentration generated by GPT and any NO
2
impurity.
Use
to move the cursor left and right and use
to increment and decrement the numeric character at the cursor.
4.
Press
to calculate and save the new high NO
2
coefficient based
on the entered span concentration.
You can change the calibration factors by using the Calibration Factors
menu. This is often useful in a troubleshooting situation. However, after
the above calibration procedure is completed, all subsequent data reduction
depends on the calibration parameters remaining the same as during the
initial calibration.
Therefore never change any calibration factor without first recording the
value so that after any troubleshooting procedure is completed, the initial
value can be re-entered thereby not altering the multipoint calibration.
The analyzer requires initial and periodic calibration according to the
procedures outlined in this manual. Initially, the frequency of the
calibration procedure should be determined by the stability of the zero and
span checks, which may be run daily. You should generate a new
calibration curve when zero and span checks indicate a shift in instrument
gain of more than 10 percent from that determined during the most recent
multipoint calibration. You can adjust the frequency of calibration and
even zero and span checks appropriately as you gain confidence with the
instrument.
Calibrate High NO
2
Zero and Span Check
