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Troubleshooting & Repair Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 283
13.2.2.4. Displayed Flow = “Warnings”
This warning means that there is inadequate gas flow. There are four conditions that might cause this:
1. A leak upstream or downstream of the flow sensor
2. A flow obstruction upstream or downstream of the flow sensor
3. Bad Flow Sensor Board
4. Bad pump
To determine which case is causing the flow problem, view the sample pressure and sample flow functions on
the front panel. If the sample pressure is reading abnormally low, then the cause is likely a flow obstruction
upstream of the flow sensor. First, check the sample filter and make sure it is not plugged and then
systematically check all the other components upstream of the orifice to ensure that they are not obstructed.
If the sample pressure is reading normal but the sample flow is reading low then it is likely that the pump
diaphragm is worn or there is an obstruction downstream of the flow sensor.
13.2.2.5. Actual Flow Does Not Match Displayed Flow
If the actual flow measured does not match the displayed flow, but is within the limits of 720-880 cm
3
/min, adjust
the calibration of the flow measurement as described in Section 12.3.4.
13.2.2.6. Sample Pump
The sample pump should start immediately after the front panel power switch is turned ON. With the Sample
Inlet plugged, the test function PRES should read about 10 in-Hg for a pump that is in good condition. The pump
needs rebuilding if the reading is above 10 in-Hg. If the test function SAMP FL is greater than 10 cm
3
/min there
is a leak in the pneumatic lines.
13.3. CALIBRATION PROBLEMS
13.3.1. MISCALIBRATED
There are several symptoms that can be caused by the analyzer being miscalibrated. This condition is indicated
by out of range Slopes and Offsets as displayed through the test functions and is frequently caused by the
following:
1. Bad span gas. This can cause a large error in the slope and a small error in the offset. Delivered from
the factory, the GFC 7001E Analyzer’s slope is within ±15% of nominal. Bad span gas will cause the
analyzer to be calibrated to the wrong value. If in doubt have the span gas checked by an independent
lab.
2. Contaminated zero gas. Excess H
2
O can cause a positive or negative offset and will indirectly affect
the slope.
3. Dilution calibrator not set up correctly or is malfunctioning. This will also cause the slope, but not the
zero, to be incorrect. Again the analyzer is being calibrated to the wrong value.
4. Too many analyzers on the manifold. This can cause either a slope or offset error because ambient
gas with its pollutants will dilute the zero or span gas.