Introduction The online residual chlorine analyzer (hereinafter referred to as the instrument) is an online water quality monitor with a microprocessor.The instrument is equipped with different types of electrodes, widely used in power plant, petrochemical industry, metallurgy, electronics, mining industry, paper industry, biological fermentation process, medicine, food and beverage, environmentally friendly water treatment, breeding and other industries, for continuous monitoring and control of the residual chlorine value of aqueous solution.Such as power plant supply water, saturated water, condensate water, general industrial water, domestic water and wastewater. The instrument adopts LCD LCD screen; intelligent menu operation; current output, free measurement range, high and low overrun alarm prompt and three groups of relay control switches, adjustable delay range; automatic temperature compensation; electrode automatic calibration methods.