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Model 9110T NOx Analyzer EPA Protocol Calibration
Teledyne Analytical Instruments 231
Note See the Troubleshooting Section 12 if there are problems.
Also see the Calibration Quality Check procedure Section 9.6.
6. After the zero and the 80% upper range limit points have been set, generate five
approximately evenly spaced calibration points between zero and 80% upper range
limit without further adjustment to the instrument.
7. Allow the instrument to sample these intermediate concentrations for about 10
minutes each and record the instrument NO and NOX responses.
8. Plot the analyzer NO and NOX responses versus the corresponding calculated
concentrations to obtain the calibration relationships.
Determine the straight line of best fit (y = mx + b) determined by the method of
least squares.
9. After the best-fit line has been drawn for the NO and the NO
X
calibrations,
determine whether the analyzer response is linear.
To be considered linear, no calibration point should differ from the best-fit line
by more than 2% of full scale.
10.7. GPT NO
2
CHECK
The 9110T computes the NO
2
concentration by subtracting the NO from the NO
X
concentration. Unlike
analog instruments, this difference is calculated by the 9110T's internal computer software. It is
extremely unlikely that the NO
2
concentration will be in error. Therefore this procedure is a confirmation
that the NO
2
subtraction algorithm in the computer is operating correctly.
IMPORTANT
IMPACT ON READINGS OR DATA
Do not make any adjustments to the instrument during this procedure.
1. Generate an NO concentration near 90% of the upper range limit.
Dilution air and O
3
generator air flows should be the same as used in the
calculation of specified conditions of the dynamic parameter according to
Section 10.5.
2. Sample this NO concentration until the NO and NOx responses stabilize. Record
the NO and NOx concentrations.
3. Turn ON and adjust the O
3
generator in the calibrator to produce sufficient O
3
to
decrease the NO concentration to about 10% of full scale.
This will be equivalent to 80% of the URL of the NO
2
channel. After the analyzer
responses stabilize, record the resultant NO, NOX, and NO
2
concentrations.
Note If the NO
X
reading should drop to less than 96% of its starting value
during this step, it indicates the NO
2
converter is in need of
troubleshooting or replacement. See Section 12.7.10 for further details.