Cathode Replacement on Polarographic DO Sensors
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.
- OxyFerm FDA Membrane Kit Ref 237140
- OxyGold Membrane Kit Ref 237135
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.
- OxyFerm Cathode Kit Ref 237306
- OxyGold B Cathode Kit Ref 237427
- OxyGold G Cathode Kit Ref 237437
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!
- OxyFerm Electrolyte Ref 237118
- OxyGold B Electrolyte Ref 237138
- OxyGold G Electrolyte Ref 237139
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.
Related Content
- Time to upgrade from Polarographic to Optical DO Measurement? See the comparison here.
- Learn about best practices for proper zero point calibration (applies to polarographic and optical DO)
- Visit our main Dissolved Oxygen Knowledge Base Page to see all articles.