Teledyne API Model 200AH NO
X
Analyzer Instruction Manual, 06492, Rev. G2
9-5
Table 9-1: Test Functions (Continued)
Test Function Factory Set-Up Comment
PMT 0-5000 mV This is the instantaneous output of the PMT. During normal
operation the value varies widely as the M200AH switches from
NO to NO
x
modes. Changes in reading will be synchronized with
valve switching. The PMT voltage values will be relatively constant
when:
1. Electric test - variation in the 2000 mV signal observed will be
sampling errors of the V/F board and preamp noise. See
Section 9.1.3.2.
2. Optic test - variation in the 100 mV signal will be PMT dark
current, preamp, HVPS plus item 1 above. See Section 9.1.3.3.
3. Sampling zero gas - signal from 1, 2 plus signal from ozone
generator air.
4. Sampling pure NO span gas - signal will be 1, 2, 3, above plus
signal from chemiluminescent reaction. Slight pulsation’s will
be noticed as the M200AH switches from NO to NO
x
. This is
due to differences in flowrates (Cv) in each channel. These
differences are taken out in the calibration process resulting in
slightly different slopes for the NO and NO
x
channels. Large
pulsation’s when switching to the NO
x
channel is indicative of
a bad converter.
5. When sampling zero gas the PMT reading should be less than
50 mV and relatively constant.
High or noisy readings could be due to:
1. Electric test - variation in the 2000 mV signal observed will be
sampling errors of the V/F board and preamp noise. See
Section 9.1.3.2.
2. Excessive background light which is caused by a possible
contaminated reaction cell.
3. Humidity (undried ambient air) in the ozone generator feed air.
4. PMT recently exposed to room light. It takes 24-48 hours for
the PMT to adapt to dim light.
5. Light leak in reaction cell.
6. Miswiring of the thermoelectric cooler causing the PMT to be
heated.
(table continued)
