Measurement principle: Turbidity is the degree of obstruction caused by suspended solids in water to the transmission of light. Water containing soil, dust, fine organic matter, and other microorganisms and colloids can cause turbidity in the water. The light waves emitted by the transmitter on the sensor are absorbed, reflected, and scattered by the measured object during transmission. Some of the transmitted light can be directed towards the detector in the 180 ° direction, while some of the scattered light can be directed towards the detector in the 90 ° direction. The intensity of light received by detectors in the 180 ° and 90 ° directions is related to the turbidity of the measured wastewater. Therefore, by measuring the intensity of transmitted and scattered light, the turbidity of the wastewater can be calculated.