Teledyne API Model 200AH NO
X
Analyzer Instruction Manual, 06492, Rev. G2
9-2
4. Pay special attention to the slopes, the slopes are the software equivalent of the span pot on
an analog instrument. If the slopes are not 1.0 0.3 the gain has changed, usually from a
change in cell pressure (vacuum) - compare to value in Table 2-1. - possible causes:
A. Partially plugged ozone killer
B. Change of pump or malfunctioning pump
C. Plugged pneumatics
D. Miss-calibration
E. Change in altitude
5. Check the AutoZero reading in the TEST functions. Compare it to the value in the factory
checkout Table 2-1. If it is significantly (>25 mV) higher, then:
A. Turn the ozone generator off (Use DIAG function). See if the AutoZero reading drops
more than 25 mV.
B. If the reading drops, the reaction cell could be contaminated. Perform the cleaning
procedure in Section 8.4.
C. If the reading remains high, there could be a light leak. Perform the procedure in
Section 8.7. High readings also occur if the PMT has been recently exposed to high light
levels, such as dis-assembly of the sensor assembly. This is normal. It usually requires
24 hours for levels to return to normal.
6. Check the Offset value in the TEST functions.
Compare it to the value in the factory checkout Table 2-1. If the reading is significantly
greater than the factory test value, the reaction cell could be contaminated or there could be a
light leak in the cell. Verify this fault by turning the ozone generator off and see if the
AutoZero reading drops more than 25 mV.
7. Perform the leak check procedure in Section 8.6. If slopes are different from each other by
> 0.3, this usually indicates a leak in the switching (NO/NO
X
) valve, partially plugged
converter, or improper calibration.
8. Incorrect span gas concentration - this could come either from wrong certificate on
calibration gas bottle, incorrect flows or setup in the calibrator, or entering the expected span
gas concentration incorrectly, see Table 7-3. If the instrument does not respond to span gas
check Section 9.2.3.
The above should get you started in diagnosing and repairing the most common faults. If these
reasons have been eliminated, the next thing to do is a Factory Calibration covered in
Section 9.1.6 or check Section 9.2 for other fault diagnosis. If difficulties persist contact our
service department. The toll free 800 telephone number is on the cover page of this manual.
9.1. Operation Verification - Diagnostic Techniques
9.1.1. Fault Diagnosis with TEST Variables
