Thermo Scientific 42i Instruction Manual page 152

Calibration
Zero and Span Check
Zero and Span Check
4-20 Model 42i Instruction Manual
1. Adjust the O generator in the GPT system to generate sufficient O
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produce a decrease in the high NO concentration equivalent to about
80% of the URL of the high NO
90% of the high NO concentration determined in the "Calibrate High
NO " procedure.
x
2. From the Main Menu, choose Calibration > Cal Hi NO2 Coefficient.
The Hi NO field displays the current NO
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NO Span Conc field is where you enter the high NO
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concentration.
3. Set the high NO calibration gas concentration to reflect the sum of the
2
NO concentration generated by GPT and any NO
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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
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.
You should have a quality control plan where the frequency and the
number of points required for calibration can be modified on the basis of
calibration and zero and span check data collected over a period of time.
Note however, that the EPA requires a minimum of one multipoint
calibration per calendar quarter. Such a quality control program is essential
range. The decrease must not exceed
2
concentration. The Hi
2
calibration gas
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impurity.
2
coefficient based
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to
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