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Troubleshooting Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 235
10.3. Calibration Problems
10.3.1. Miscalibrated
There are several symptoms that can be caused by the analyzer being miss-calibrated. 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 7000TA’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
and 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.