Table of Contents
Advertisement
Teledyne ML - T100 UV Fluorescence SO2 Analyzer
10.3.2. HIGH FLOW
10.4. CALIBRATION PROBLEMS
10.4.1. NEGATIVE CONCENTRATIONS
A slight, negative signal is normal when the analyzer is operating under zero gas and the
signal is drifting around the zero calibration point. This is caused by the analyzer's zero noise
and may cause reported concentrations to be negative for a few seconds at a time down to -5
ppb, but should alternate with similarly high, positive values.
Mis-calibration is the most likely explanation for negative concentration values. If the zero air
contained some SO
analyzer was calibrated to that concentration as "zero", the analyzer may report negative
values when measuring air that contains little or no SO
analyzer was zero-calibrated using ambient air or span gas.
If the response offset test function for SO
or high voltage supply, or sample chamber contamination, could be the cause.
10.4.2. NO RESPONSE
Confirm response by supplying SO
Check the sample flow rate for proper value.
To check the actual sample flow, disconnect the sample tube from the sample inlet on the
rear panel of the instrument. Ensure that the unit is in basic SAMPLE mode. Place a
finger over the inlet and see if it gets sucked in by the vacuum or, more properly, use a
flow meter to measure the actual flow. If a proper flow of approximately 650 cm³/min
exists, contact customer service. If there is no flow or low flow, continue with the next
step.
Check that the sample pressure is at or around 28 (or about1 in-Hg-A below ambient
atmospheric pressure).
Flows that are significantly higher than the allowed operating range (typically ±10-11%
of the nominal flow) should not occur in the M unless a pressurized sample, zero or span
gas is supplied to the inlet ports. Be sure to vent excess pressure and flow just before the
analyzer inlet ports.
When supplying sample, zero or span gas at ambient pressure, a high flow would indicate
that one or more of the critical flow orifices are physically broken (very unlikely case),
allowing more than nominal flow, or were replaced with an orifice of wrong
specifications. If the flows are more than 15% higher than normal, we recommend that
the technician find and correct the cause of the flow problem,
This section provides information regarding possible causes of various calibration
problems.
Negative concentration values may be caused due to the following:
gas (contaminated zero air or a worn-out zero air scrubber) and the
2
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,
06807A(DCNxxxx)
. The same problem occurs, if the
2
(OFFSET) are greater than 150 mV, a failed PMT
2
span gas of about 80% of the range value to the analyzer.
2
Troubleshooting & Repair
269
Advertisement
Table of Contents
