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The Measuring Principle and Daily Maintenance of the Dissolved Oxygen Meter

Dissolved oxygen analyzer measurement principle: the solubility of oxygen in water depends on temperature, pressure and dissolved salts in water. The sensing part of the dissolved oxygen analyzer is composed of gold electrode (cathode) and silver electrode (anode) and potassium chloride or potassium hydroxide electrolyte. Oxygen diffuses through the membrane into the electrolyte and the gold electrode and silver electrode constitute a measurement loop. When a polarization voltage of 0.6 ~ 0.8V is applied to the electrode of the dissolved oxygen analyzer, oxygen diffuses through the membrane, the cathode releases electrons, the anode accepts electrons, and a current is generated. The entire reaction process is: anode Ag+Cl→AgCl+2e- cathode O2+2H2O+4e→4OH- According to Faraday’s law: the current flowing through the electrode of the dissolved oxygen analyzer is proportional to the oxygen partial pressure, and there is a linear relationship between the current and the oxygen concentration at the same temperature.

The daily maintenance of the dissolved oxygen analyzer includes regular cleaning, calibration and regeneration of the electrodes.

⑴ The electrode should be cleaned once every 1 to 2 weeks. If there are pollutants on the diaphragm, it will cause measurement errors. Be careful when cleaning, taking care not to damage the diaphragm. Rinse the electrode in clean water. If the dirt cannot be removed, wipe it carefully with a soft cloth or cotton cloth.

⑵ The zero point and span should be re-calibrated in February to March.

(3) The regeneration of the electrode is about once a year. When the measurement range cannot be adjusted, the dissolved oxygen electrode needs to be regenerated. Electrode regeneration includes replacing the internal electrolyte, replacing the diaphragm, and cleaning the silver electrode. If the silver electrode is oxidized, it can be polished with fine sandpaper.

⑷ If the electrode leaks during use, the electrolyte must be replaced.

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