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A common maintenance task with polarographic DO sensors is replacement of the cathode. The steps below help to guide you through it:

Disassembly of Polarographic DO Sensor

Put the sensor in an upright position and carefully unscrew the membrane cartridge.

Flush the replaceable cathode with deionized water, then dry the metal parts. Do not touch anode and cathode.

Hold the cathode on the metal part (B) in front of the thread (A) and the sensor on the shaft (C) and pull apart. Just pull, do not turn!

Please check that all contacts are dry and clean.

Replacement of Cathode

Replace cathode with a new one. Rotate the cathode until the correct position is found and then push the cathode into the shaft.

Reassembly of Polarographic DO Sensor

Check the small O-ring above the glass body of the cathode. Replace if damaged.

Use the plastic pipette of the membrane kit to pipette approximately 1 to 1.2 ml of electrolyte into the new membrane cartridge. The pipette must NOT touch the membrane itself!

Carefully screw the cartridge onto the sensor shaft. Any spillage of electrolyte should be rinsed away with water.

After completion of this procedure the sensor should be reconnected to the cable and normal polarization and calibration procedures should be followed.

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