About The Principles And Classification Of Dissolved Oxygen Meters

The dissolved oxygen analyzer is based on the principle of electrochemistry, that is, a redox reaction will occur on two different metal electrodes in the electrolyte solution containing oxygen, and the resulting diffusion current and oxygen concentration in the solution will An instrument for measuring the oxygen content in water based on the principle of a certain relationship. Some instruments also use the polarographic method in voltammetry. After applying a voltage to the working electrode in the solution, the current on the polarogram generated has a certain relationship with the concentration of the measured substance in the solution.

The dissolved oxygen analyzer can be used to measure the dissolved oxygen content in the aqueous solution of the sample being tested on-site or in the laboratory. Since dissolved oxygen is one of the main indicators of water quality, the dissolved oxygen analyzer can be widely used to measure dissolved oxygen content in various situations, especially in aquaculture water, photosynthesis and respiration, and on-site measurements. When evaluating the ability of streams and lakes to support biological survival, biochemical oxygen demand (BOD) testing is performed, measuring a sample aqueous solution containing organic matter that consumes oxygen as it becomes putrefactive, and determining the dissolved oxygen concentration and sample aqueous solution relationship between temperatures. 

A dissolved oxygen meter actually measures the amount of oxygen dissolved in an aqueous solution. Oxygen is dissolved in water through surrounding air, air movement, and photosynthesis. Dissolved oxygen electrodes can be used to measure and monitor processes where oxygen content affects reaction speed, process efficiency, or the environment. The dissolved oxygen meter has the characteristics of easy installation, a long calibration cycle (3 to 4 months), insensitivity to other substances, and the ability to monitor the use of the coating and internal electrolyte. Generally, the electrolyte and coating are replaced every one to three years.

Proper dissolved oxygen is essential for good water quality, and all life forms require oxygen. The natural stream water purification process requires the proper oxygen content to supply aerobic life forms. If the oxygen content in the water is lower than 5.0 mg/L, it will be difficult for aquatic organisms to survive. The lower the concentration, the more difficult it is. If the oxygen content is lower than 1-2 mg/L and continues for several hours, a large number of aquatic organisms will die.

Dissolved oxygen meters are also divided into several categories:

1. Classified by use: portable dissolved oxygen meter, desktop dissolved oxygen meter and pen-type dissolved oxygen meter.

2. Classified by portability: laboratory dissolved oxygen meter, industrial online dissolved oxygen meter, etc.

3. Other categories: economical dissolved oxygen meter, intelligent dissolved oxygen meter, precision dissolved oxygen meter or divided into pointer type dissolved oxygen meter and digital display type dissolved oxygen meter.

Dissolved oxygen analyzer precautions:

1. Calibrate once a day before use, using the water-saturated gas method. Even if the machine is turned off within a day, there is no need to calibrate it again;

2. The temperature difference between calibration and measurement should not be too large, preferably no more than +-5℃;

3. The reading is abnormal and the dissolved oxygen analyzer diaphragm must be replaced (such as if the reading is unstable after starting up or does not become stable from high to low);

4. When replacing the membrane of the dissolved oxygen analyzer, the electrolyte should be free of bubbles, the membrane should not be wrinkled, and the excess membrane should be cut off;

5. When the sensor electrolyte dries, the dissolved oxygen membrane must be replaced;

6. When replacing the dissolved oxygen membrane, wash away the old electrolyte with deionized or distilled water, add 2-3 drops of the new electrolyte and let it dry. Ordinary dissolved oxygen sensors should be filled with new electrolyte until the liquid level bulges and the dissolved oxygen film should be pressed tightly without leaving any bubbles; the cover film should be filled with half the amount of new electrolyte and tightened;

7. It can be used after the cover film is replaced. After replacing the ordinary film, it should be left overnight to allow the film to restore balance;

8. The surface of the dissolved oxygen membrane should be cleaned carefully to avoid damaging the membrane;

9. It is recommended to replace the dissolved oxygen membrane every 2-4 weeks, but if the water quality is good and properly maintained, the dissolved oxygen membrane can even be replaced every six months, provided that the calibration reading is normal every time;

10. If bubbles continue to appear at the bottom during measurement, the sensing head should be pointed upward and tied to the cable. The bubbles should not stay on the surface of the dissolved oxygen film;

11. The dissolved oxygen analyzer needs to be stirred when measuring. Proper stirring is conducive to obtaining true dissolved oxygen readings. Rapid pulse method and microelectrode array measurements without stirring.

Boqu Instrument is a professional water quality analyzer supplier and manufacturer in China, with more than 10 years of dissolved oxygen analyzer manufacturing experience, welcome to visit our factory!