Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 268)

Model 9110TH NOx Analyzer Troubleshooting & Repair
Teledyne Analytical Instruments 248
9. Set the HVPS coarse adjustment switch to the lowest setting that will give you just
above 3600 mV NORM PMT signal. The coarse adjustment typically increments
the NORM PMT signal in 100-300 mV steps.
Figure 7-17: Pre-Amplifier Board Layout
10. Adjust the HVPS fine adjustment such that the NORM PMT value is 3600-3700 mV.
The fine adjustment typically increments the NORM PMT value by about 30 mV.
It may be necessary to go back and forth between coarse and fine adjustments if the
proper value is at the threshold of the min/max coarse setting.
Note Do not overload the PMT by accidentally setting both adjustment
switches to their maximum setting. Start at the lowest setting and
increment slowly. Wait 10 seconds between adjustments..
11. If the NORM PMT value set above is now between 3560-3640 mV, skip this step.
Otherwise, adjust the NORM PMT value with the gain potentiometer down to
3600±10 mV.
This is the final very-fine adjustment.
12. that during adjustments, the NORM PMT value may be fluctuating, as the analyzer
continues to switch between NO and NO
X
streams as well as between measure and
AutoZero modes.
You may have to mentally average the values of NO and NO
X
response for this
adjustment.
13. Perform a software span calibration (Section 5.3, 7.4, or 7.6) to normalize the
sensor response to its new PMT sensitivity.
14. Review the slope and offset values, the slopes should be 1.000±0.300 and the
offset values should be 0.0±20 mV (-20 to +150 mV is allowed).