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SZ10T Consort Dissolved Oxygen electrode


The SZ10T dissolved Oxygen electrode is a MPOD (Membrane-covered Polarographic Oxygen Detector) system. This model is a galvanic type. The external portion of the electrode is constructed of stainless steel or Delrin. The internal portion of the electrode is constructed of 316 L stainless steel enclosing a Lead anode and a Platinum cathode. A thin Teflon-FEP membrane, provides for efficient sealing of the cathode/anode and electrolyte within the cylinder. The membrane is permeable to Oxygen but impermeable to water and electrolyte.

The mechanical construction is shown in this picture:

  1. Electrode cap (material Nylon) with cable/body connection
  2. Electrode body (Delrin)
  3. Temperature sensor (for older system). The latest electrodes have this sensor built in the inner electrode stem
  4. Inner electrode stem
  5. Anode (Lead)
  6. Cathode (Platinum)
  7. Capsule with membrane (Teflon)
  8. Membrane cap (Delrin) with internal O-ring

Start Up

  • Unscrew the membrane cap (8) from the electrode body (2).
  • Clean it with distilled water (DI water).
  • Fill the membrane cap with the electrolyte to a level above the membrane cartridge using the syringe provided. Hold the electrode in an upright position and gently screw the cap back onto the body. Make sure there remain no air bubbles in it.
  • Please inspect the membrane for tears or leakage. The membrane should be uniformly stretched across the inner body. Replace the membrane if any damage has occurred.
  • Let the electrode rest for a while to polarise. This can be followed by reading the output value with the meter. It is required to wait until the measurement has stabilised. This can take several hours.

Now the electrode should be ready for use. Start and complete the calibration procedure following the manual of the device, before starting the measurements.

Mind that after disassembling/reassembling the electrode for any reason, this procedure should be followed again.

The electrolyte may be worn out after some time of use, or dried out when left in air for some time. Then it is required to replenish it the same way as here described.

Placement of the membrane capsule

Check the correct position of the O-ring, insert the capsule and push it to its final position using the supplied stick, check the membrane.

Zero point

The zero current of the O2 electrode is usually negligibly small. Nonetheless, the electrode zero point should be periodically checked as some electrode faults result in an excessive zero current. Checking the zero point is necessary before the measurement of low oxygen concentration.

Zero point checking may be effected in both pure nitrogen and in water saturated with nitrogen. An alternative is the use of a freshly prepared 2% bisulfite solution.

The saturation of water with nitrogen takes several minutes. Checking with pure nitrogen gas is faster and more reliable. The zero point can be read after about 5 minutes.


Calibration is usually effected at Oxygen saturation since it is the easiest method. Calibration causes the DO reading to be adjusted to 100% saturation. As it is dependent on pressure, the calibration should be effected under operating pressure.

The preferred method for calibrating an Oxygen electrode is using air-saturated water. Alternatively can it be also done in the air that is water saturated (100% humidity). Always mind that the temperature and the air pressure influences the calibration and the measurements. So take care of stable environment conditions for the electrode.

Saturate distilled water in a vessel by purging air in it for approximately 20 minutes to create 100% air saturation. Perform the saturation of the solution under operating pressure. Allow the output signal to stabilise. Follow the instructions of the meter to calibrate the electrode at 100% saturation.


The electrode requires only little maintenance but should be checked regularly. Normal cleaning/rinsing of the body and replenishment of the electrolyte (see Start Up) should mostly be sufficient. Mind that the use in some environments (e.g. algae) might block the membrane and that regular adequate cleaning will be required.

After the electrode has been used for a period of time, the residual current may rise (see Zero point). To reduce the residual current, the following cleaning method is recommended.

  1. Carefully unscrew the membrane cap from the body.
  2. Rinse the inside of the membrane cap with DI water.
  3. Soak the Lead anode in 0.1N HCl (Do not use aqua regia!) for 15 to 20 minutes. Rinse thoroughly with DI water, blot dry with tissue paper.
  4. Mix soap, water and a few drops of ammonia together in a container. Brush the cleaning solution onto the tarnished Platinum with care. Use an old toothbrush or other soft-bristled brush. Work gently to get rid of the tarnish.
  5. Rinse the soaked portions thoroughly with DI water. Blot dry with tissue paper.
  6. Reassemble the electrode according to the method described in Start Up.
do_issues.1427804829.txt.gz · Last modified: 31/03/2015 12:27 by pieter