The measurement principle of the online turbidity monitor is based on the surface scattering method. That is, a beam of light is directed into the solution to be tested, the beam is scattered by the suspended particles in the water sample, and the receiver is placed in a direction 90° from the beam to receive the scattered light. The light energy of the scattered light reaching the receiver is proportional to the turbidity in the solution. The receiver converts the light energy into an electrical signal. After the signal is amplified, it enters the central processing unit, performs calculation and outputs the result. The online turbidity monitor adopts a wall-mounted structure, and its interior is composed of a solenoid valve, a sampling flow cell, a light source, a photoelectric converter, a main control board, and a liquid crystal display. Water collection is controlled by a solenoid valve, and the solenoid valve is turned on during measurement to collect water samples into the flow cell for measurement. The light source adopts a pulsed light emitting diode, which emits light to irradiate the flow cell, and a high-sensitivity photodiode is installed in a direction perpendicular to the incident light to detect the intensity of scattered light. Basic maintenance of online turbidity monitor: Clean the measurement chamber regularly according to the water quality on site; When the turbidity value is ≤5NTU, check the dirt in the measurement chamber every month, and clean it if necessary. When the turbidity value is >5NTU, check the dirt in the measurement chamber every week and clean it if necessary. After removing the measuring head of the online turbidity monitor, use a brush to clean the measuring chamber. After cleaning, use the emptying valve at the lower part to empty the cleaning liquid. If there is algae growth, it can be disinfected with algaecide or sodium hypochlorite solution, and it can be used normally after rinsing with pure water. When it is left unused for a long time, please empty the water in the chamber of the turbidity monitor to avoid the growth of bacteria and affect the measurement results in the future.