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| Flue Gas Analysis System | Maintenance & Troubleshooting 5 | |
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When subjecting the analyzer circuits to checkout, it is appropriate to first check the power supplies for correct output. If voltages are incorrect, then take corrective action with power supply components .
5.2.2Oxygen Analyzer Section 5.2.2.1 Inability to Calibrate
If the oxygen analyzer cell circuit exhibits insufficient amplifier gain, or if it is impossible to adjust the output signal with the SPAN potentiometer, the oxygen cell is probably used up. This process will require some time; it will not happen immediately. Before replacing the cell, however, check the sample circuit to make sure that the sample is actually getting to the cell.
If the cell is functional, or there is still no output with installation of a new cell, then a check of the electronics should he undertaken.
•First, check the power supply. Make sure that proper voltages exist at
•If voltages are satisfactory, check output of A1 at pin 6. (It will be easier to check the output of A1 at the tiepoint of resistors R1/R2/R3.) Use the tiepoint of C7 and C8 as the power common. The voltage (output of A1) should be 0.125 V with a full scale signal. If the oxygen cell is exposed to 20.9% oxygen, the voltage at
•If the voltage at
In addition to possible malfunctions occurring in Al and/or A2, the FET (Q1) could be malfunctioning, i.e., not being turned off. If Q1 is “on” all the time, the oxygen cell will be shorted and no signal will be able to get through the feedback resistors for A1.
TELEDYNE BROWN ENGINEERING |
Analytical Instruments