This standard specifies in detail the requirements of diaphragm-free electrode dissolved oxygen meters, including technical specifications, test methods, inspection rules and signs, Encasement, transportation and storage, etc. It is suitable for on-line dissolved oxygen meters using diaphragm-free electrodes for continuous measurement of dissolved oxygen concentration in water. A series of relevant standards are cited to ensure equipment safety and Reliability. The dissolved oxygen meter consists of measurement electrodes and electronic units. It works based on the principle of electrochemistry and is capable of accurate measurement of dissolved oxygen concentration in water samples. The results are displayed in the way of display and Output signal.