Walchem WebMaster ONE Instruction Manual page 159

pH Calibration Failure
This error message occurs after attempting an electrode calibration. The normal slope of a pH
electrode is 59 mV/pH unit. As the electrode ages, this slope will decrease. The WebMasterONE
reports the % difference from the theoretical slope after each calibration. When the slope reaches
12 mV/pH unit (80% difference), the calibration fails.
Possible Causes
Dirty electrode.
Faulty electrode cartridge.
Sensor cable disconnected.
Faulty electrode housing.
Faulty core interface circuit board
(if Sensor 1).
Faulty sensor option circuit board
(if Sensors 2-4).
ORP Calibration Failure
This error message occurs after calibrating the ORP electrode. If the difference between the raw
mV reading and the calibrated value exceeds 50%, then the calibration will fail.
Possible Causes
Dirty electrode.
Faulty electrode cartridge.
Sensor cable disconnected.
Faulty electrode housing.
Faulty core interface circuit board
(if Sensor 1).
Faulty sensor option circuit board
(if Sensors 2-4).
Corrective Actions
Clean electrode and recalibrate as described in
Section 7.3 above.
Replace cartridge.
Reconnect cable. Also ensure that the electrode
cartridge is tightly screwed into the electrode
housing, and that the inside of the housing is
dry. Make sure that the +/- 5 VDC and the IN-,
IN+ wires are firmly attached.
If the controller passes self test, the wiring is
correct, the +/- 5 VDC signal is present and
the cartridge is attached and OK, replace the
electrode housing.
Replace the core interface board.
Replace the sensor option board.
Corrective Actions
Clean electrode and recalibrate as described in
Section 7.4 above.
Replace electrode cartridge.
Reconnect cable. Also ensure that the electrode
cartridge is tightly screwed into the electrode
housing, and that the inside of the housing is
dry. Make sure that the +/- 5 VDC and the IN-,
IN+ wires are firmly attached.
If the controller passes self test, the wiring is
correct, the +/- 5 VDC signal is present and
the cartridge is attached and OK, replace
electrode housing.
Replace the core interface board.
Replace the sensor option board.
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