Industrial dissolved oxygen meter electrochemical measurement method
The oxygen content in water can fully indicate the degree of self-purification of water. For biological treatment plants that use activated sludge, it is very important to understand the oxygen content of the aeration tank. The increase in dissolved oxygen in the sewage will promote biological activities other than anaerobic microorganisms, thereby removing volatile substances and easily oxidized naturally. ions to purify sewage.
There are three main methods for measuring oxygen content with industrial dissolved oxygen meters: automatic colorimetric analysis and chemical analysis measurement, paramagnetic method measurement, electrochemical method measurement, and fluorescence method. The amount of dissolved oxygen in water is generally measured using electrochemical methods.
Oxygen is soluble in water, and its solubility depends on temperature, total pressure at the water surface, partial pressure, and dissolved salts in the water. The higher the atmospheric pressure, the greater the water's ability to dissolve oxygen. The relationship is determined by Henry's Law and Dalton's Law. Henry's Law states that the solubility of a gas is proportional to its partial pressure.
The oxygen measurement sensor consists of a cathode, a counter electrode with current, and a reference electrode without current. The sensor is covered by a diaphragm. The coating separates the electrode and electrolyte from the liquid being measured. Only dissolved gases can penetrate the coating, thus protecting the The sensor can not only prevent the electrolyte from escaping, but also prevent the intrusion of foreign substances from causing contamination and poisoning.
The size of the current is proportional to the oxygen partial pressure of the measured sewage. This signal, together with the temperature signal measured by the thermal resistor on the sensor, is sent to the transmitter. The oxygen content stored in the sensor is used to calculate the relationship between the oxygen partial pressure and temperature. The oxygen content in the water is calculated using the relationship curve, and then converted into a standard signal output. The function of the reference electrode is to determine the cathode potential.
