Thermo 42i - Page 139

Calibration
Calibration
Thermo Electron Corporation Model 42i Low Source Instruction Manual 4-11
or imbalance), or the converter needs replacement or servicing. The
NO
2
analog output will reflect the NO
2
concentration generated by
GPT, any NO
2
impurity, and the NO
2
zero offset.
The recorder response will be as follows:
Where:
URL = Nominal upper range limit of the NO
2
channel, ppm
12. Record the NO
2
concentration and the analyzer's NO
2
response.
13. Maintaining the same F
NO
, F
O
, and F
D
, adjust the ozone generator to
obtain several other concentrations of NO
2
over the NO
2
range (at least
five evenly spaced points across the remaining scale are suggested).
14. Record the stable responses and plot the analyzer's NO
2
responses
versus the corresponding calculated (using the above equation for
[NO
2
]
OUT
) concentrations and draw or calculate the NO
2
calibration
curve.
Note It is important that the curve should be linear within ±1% FS over the
NO
2
range. If the curve is nonlinear, the analyzer is not operating correctly,
(possible leak, or converter failure, etc.), and should be serviced. Assuming
the curve is linear, subsequent data should be reduced using this NO
2
calibration curve response.

Using the Calibration Factors menu can change the calibration factors. 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. 
Z
+100 x
URL
]
NO
[
=scale)(%ResponseRecorder
NO
OUT
2
2