Design And Implementation Of A Throw-in Turbidimeter With Near Infrared Light

Water is an indispensable resource for production and daily life,but the current water pollution in the worid is serious.Turbidity refers to the degree of hindrance that light passes through a solution.The spread of many diseases is caused by the adhesion of some viruses and bacteria to the fine particles,which reduces the disinfection of water by ozone and chloride ions.Therefore,the protection and improvement of water environment has become a global issue.Turbidity is one of the important indicators in water quality testing,and the measurement of turbidity is very important.To solve the above problems,this paper designed a throw-in turbidimeter based on near infrared light with a measurement range of 0-1000 NTU,and the outline of this paper is as follows:(1)The basic principles of turbidity measurement are introduced,including Lambert-Beer law and the scattering of light by water samples.We analyzed the methods of turbidity detection including transmission method,scattering method and ratio method.A proper measurement method suitable for this paper was selected.(2)The selection of light source and photodetector was completed,and the structure of the turbidimeter test probe was designed by the software of SolidWorks,and we also found a effective way to seal the test probe.(3)According to the requirements of the turbidimeter,the STM32 MCU was selected as the main chip of the proposed system,which is suitable for high performance,low cost and low power in embedded application.The design of hardware system for the turbidimeter was completed by Altium Designer software.The hardware circuit is mainly composed of I/V conversion circuit,amplification circuit,filter circuit,display circuit and E~2PROM circuit.(4)The design of hardware system for the turbidimeter was developed based on the Keil uVision4 environment.The main modules include initialization module,sampling and data processing module,calibration module and human-computer interface module.(5)We completed the design of turbidimeter shell and the preparation of the turbidity standard solution.The test of test probe was carried out to analyze the stability.The calibration work of the instrument was conducted to analyze the performance of turbidimeter.Compared with the traditional turbidimeter,the proposed turbidimeter has the advantages of simple measurement,simple circuit structure,and low power consumption.The experimental results show that the designed turbidimeter has high sensitivity,good measurement repeatability and high measurement accuracy,and it is conducive to practical applications.