Walchem WebMaster Instruction Manual download pdf (Page 107)

103

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 WEBMASTER

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 Corrective Actions

Dirty electrode. Clean electrode and recalibrate as described in

Section 7.3 above.

Faulty electrode cartridge. Replace cartridge.

Sensor cable disconnected. 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.

Faulty electrode housing. 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.

Faulty sensor option board. Replace the sensor option circuit board.

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 Corrective Actions

Dirty electrode. Clean electrode and recalibrate as described in

Section 7.4 above.

Faulty electrode cartridge. Replace electrode cartridge.

Sensor cable disconnected. 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.

Faulty electrode housing. 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.

Faulty sensor option board. Replace sensor option circuit board.

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Walchem WebMaster Instruction Manual Page 107