Teledyne API Model 200AH NO
X
Analyzer Instruction Manual, 06492, Rev. G2
9-28
9.2.7. Unstable Zero
Common causes are:
1. Leak in pneumatic system.
2. Light leak - check the sensor module with strong light.
3. Sample lines or sample filter dirty - clean or replace.
9.2.8. Inability to Span
If the SPAN button is not illuminated when attempting to span, that means the reading is outside
of the software gain ranges allowed. In an analog instrument it would be the equivalent to the
span pot hitting the rotation stop.
Here are some things to check:
1. Check the expected span concentration values in CAL-CONC-NOX and CAL-CONC-NO,
and compare them to the concentration of the calibrator span gas being input. They should be
equal.
2. When sampling span gas, check the PMT - TEST function reading. The mV reading should
be 8x the expected span concentration in step 1. above for range settings up to 500 ppm. If
over 500 ppm the value should be 0.8x the expected span concentration.
For example, if the expected span gas concentration is 80 ppm, the PMT reading should be
8 * 80 = 640 mV 30%.
3. Check ET and OT for the correct response.
4. If the above do not check out, perform the Factory Calibration Procedure Section 9.1.6.
9.2.9. Inability to Zero
If the ZERO button is not displayed when attempting to zero, that means the reading is outside of
the software gain ranges allowed. In an analog instrument it would be the equivalent to the zero
pot hitting the rotation stop.
Here are some things to check:
1. Select the PMT - TEST function. With zero gas going into the instrument, the value should
be less than 25 mV, a number close to 0 mV is common. If you are getting a high reading
here the probable reasons are:
