8.3 Calibration Errors
The MAXO2 analyzers have a self test feature built into the software to detect faulty calibrations. During calibration, if the signal from the oxygen sensor is outside the limits stored within the instrument’s memory, a flashing “CAL Er” is displayed. The error code is displayed to indicate that either the sensor should be replaced or that there is a fault in the calibration process. A few simple hints can prevent calibration errors.
If you try to adjust the analyzer display before the reading has stabilized, the “CAL Er” may appear. For example, if the analyzer had just been calibrated on a known high concentration of oxygen source gas and then exposed to ambient air, you should wait until the reading has stabilized. If you try to adjust the display to read 20.9% before the sample line has cleared of high concentration O2, the sensor may actually be exposed to residual high % oxygen. The signal from the sensor would still be high and considered “out of spec” for air, thus resulting in a “CAL Er”. The proper procedure is to wait for the reading to stabilize before adjusting the display. This may take 30 seconds or more.
8.4 Atmospheres of High Humidity
The MAXO2 analyzer can be used in applications where the relative humidity of the sample gas ranges from 0 to 95%,
For example, if the MAXO2 analyzer is calibrated in dry gas and then the gas is humidified, the analyzer will correctly display a reading which is slightly lower than previously displayed. This is due to the dilution of oxygen in the sample gas by water vapor.
Gas streams of high humidity may tend to condense on the sensor. Condensation on the sensor may eventually affect performance. For this reason, it is recommended that the unit be used in a vertical position, with the barb fitting pointing downward to prevent condensate from flowing onto the sensing surface.
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