A transmission turbidity measurement system with wide dynamic range based on single photon detection technology

A turbidity measurement system based on single photon detection technology has been developed to measure the turbidity of high turbidity water in industrial wastewater. The transmitted light measurement based on the Beer-Lambert principle is used to expand the measurement range. The avalanche photodiode (APD) based highly sensitive single photon detection technology is used to obtain the total intensity of transmitted light and quantize it to the corresponding photon number, which can improve the sensitivity and response speed of the proposed system. In order to maximize the turbidity measurement range and improve accuracy, different incident optical powers are used for the measurement of low turbidity and high turbidity respectively. It has been experimentally verified that the turbidity in the range of 100 NTU to 4000 NTU can be effectively measured when the incident optical power is 10 mw. When the low turbidity is measured, the incident light power should be set as low as 0.3mw, which is suitable for the turbidity measure between 10NTU to 100NTU.The proposed turbidity measurement system has a strong applicability and can be applied to industrial water turbidity measurement.