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Troubleshooting & Service Model T101 Instruction Manual
222
If the response offset test function for H
2
S (H2S OFFS) are greater than
150 mV, a failed PMT or high voltage supply, or sample chamber
contamination, could be the cause. Clean the sample chamber according
to Section 8.3.6.
9.3.2. NO RESPONSE
If the instrument shows no response (display value is near zero) even though sample gas
is supplied properly and the instrument seems to perform correctly,
Confirm response by supplying H
2
S span gas of about 80% of the range
value to the analyzer.
Check the sample flow rate for proper value.
Check for disconnected cables to the sensor module.
Carry out an electrical test with the ELECTRICAL TEST (ETEST)
procedure in the diagnostics menu, see Section 4.6.5. If this test
produces a concentrati
on reading, the analyzer’s electronic signal path is
working.
Carry out an optical test using the OPTIC TEST (OTEST) procedure in
the diagnostics menu, see Section 4.6.4. If this test results in a
concentrati
o
n signal, then the PMT sensor and the electronic signal path
are operating properly. If the T101 passes both ETEST and OTEST, the
instrument is capable of detecting light and processing the signal to
produce a reading. Therefore, the problem must be in the pneumatics,
optics or the UV lamp/lamp driver.
9.3.3. UNSTABLE ZERO AND SPAN
Leaks in the T101 or in the external gas supply and vacuum systems are the most
common source of unstable and non-repeatable concentration readings.
Check for leaks in the pneumatic systems as described in Section 9.5.1.
Consider pneumatic components in the gas delivery system outside the
T101 such as a change in zero air source (ambient air leaking into zero
air line or a worn-out zero air scrubber) or a change in the span gas
concentration due to zero air or ambient air leaking into the span gas
line.
Once the instrument passes a leak check, do a flow check (Section 9.5.2)
to make s
u
re that the instrument is supplied with adequate sample gas.
Confirm the UV lamp, sample pressure and sample temperature readings
are correct and steady.
Verify that the sample filter element is clean and does not need to be
replaced.
9.3.4. INABILITY TO SPAN - NO SPAN BUTTON
In general, the T101 will not display certain keyboard choices whenever the actual value
of a parameter is outside of the expected range for that parameter. If the calibration
menu does not show a SPAN button when carrying out a span calibration, the actual
concentration must be outside of the range of the expected span gas concentration,
which can have several reasons.
07266B DCN6485