Teledyne API Model 200AU NOX Analyzer Instruction Manual, 02293, Rev. F
7-23
7.6.6 Moly Converter Efficiency The moly efficiency should be 96 to 102% efficient. If it is outside these limits it should be
replaced. The converter efficiency can be determined from the data collected in Section 7.6.5.3.
For each NO2 concentration generated:
1. Calculate the concentration of NO2 converted as:
[NO ] = [NO ] - ([NO ] - [ NO ] Equation -11
2CONV 2OUT xORIG xREM
)7
Where:
[NOx]ORIG is the NOx concentration before the GPT ozone is turned on, and [NOx]REM is the
NOx remaining after GPT.1
2. Plot the [NO2]CONV concentration output by the instrument on the y-axis against the
concentration generated [NO2]OUT on the x-axis. The plot should be a straight line within the
± 2% linearity criteria given for the NOx and NO channels.
3. Determine the best straight line fit of the plot either by inspection or least squares. The
slope of the resulting straight line is the moly efficiency. The value should be between .96
and 1.02. If not, the moly needs to be replaced.
4. If you want the M200AU to automatically compensate (Section 7.6.6.1) for converter
efficiency, enter the efficiency value in the front panel by CAL-CONC-MOLY-SET, then
key in the slope from step 3 followed by ENTR. Press EXIT to return to the SAMPLE menu.
7.6.6.1 Automatic Moly Converter Efficiency Compensation
The M200AU can automatically compensate the NOx and NO2 readings for the molybdenum
converter efficiency. There are 2 ways to enter the converter efficiency into the instrument. The
first is to enter the efficiency as a decimal fraction using the CAL-CONC-MOLY-SET menu.
The second method is to have the M200AU compute the efficiency using the CAL-MOLY-CAL
menu. The procedure is given in Table 7-14. To disable the compensation, press CAL-CONC-
MOLY-SET and enter 1.0000 as the efficiency.