Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
7-21
The analog voltage output should measure 80% of the voltage range selected. (e.g. 4.00VDC if
0-5V output is selected.) The readings on the front panel display should be equal to the expected
NO and NO
x
concentrations entered in the procedure given in Table 7-13. See the
Troubleshooting Section 9.2.8 if there are problems. Also see the Calibration Quality Check
procedure Section 7.8.
After the zero and the 80% URL points have been set, generate five approximately evenly
spaced calibration points between zero and 80% URL without further adjustment to the
instrument. Allow the instrument to sample these intermediate concentrations for about 10
minutes each and record the instrument NO and NO
x
responses.
Plot the analyzer NO and NO
x
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.
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.
7.6.5.3 GPT - NO
2
Calibration Procedure
The M200AU computes the NO
2
concentration by subtracting the NO from the NO
x
concentration. Unlike analog instruments, this difference is calculated by the M200AU's internal
computer software. It is extremely unlikely that the NO
2
concentration will be in error if the NO
and NO
x
channels are calibrated correctly. Therefore this procedure is a confirmation that the
NO
2
subtraction algorithm in the computer is operating correctly.
NOTE
During this procedure do not make any adjustments to the instrument.
1. Generate a NO concentration near 90% of the URL. 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 7.6.4. Sample this NO concentration until the NO and NO
x
responses stabilize. Record the NO and NO
x
concentrations.
