Design And Implement Of The Optical Turbidimeter Based On STM32 Microcontroller

The turbidity is an important technical parameter which is used to reflect the clarity or turbidity of water.Turbid water is mainly caused by water which is including sediment,bacteria,microorganisms,suspended particle,colloids,other organism and inorganic matter.These impurities directly affect the quality of water,and may also cause infectious diseases.In view of the above problems of water pollution,a photoelectric turbidimeter based on STM32F103 microcontroller is designed in this thesis.It can measure turbidity of water quickly and accurately,and has important practical significance for water quality measurement.The overall design of the photoelectric turbidimeter is given by the paper,including the light path design,the hardware circuit design and the software system design.In the process of light path design,the selection of sensors which is including the design of light source,photoelectric detector and water slot,is analyzed and demonstrated respectively.In the hardware circuit design,in order to reduce the influence of noise from the source,voltage drive circuit is designed to make the light source more stable and reliable.Optical signal is converted to current signal by photoelectric detector,and then is convert to voltage signal through the I/V conversion circuit finally.Through amplifying and filter circuit,the signal is sampled and processed by STM32F103 microcontroller.In the software design,according to the nature of turbidity,tiny suspended particles are constantly doing Brown motion in the process of measurement,while the suspended solids of large particles is sinking to the bottom of the water slot quickly,resulting in the instability of the measurement results.It needs to add median filtering and sliding window algorithm in the tuidibity system for making the measurement result more stable and accurate.In order to improve the user experience,the tuidibity system also designed a human-computer interface,which has the functions of saving the measurement results and searching history records.Finally,the experimental results is analysed in this thesis: In the low turbidity range of 0-400 NTU,it's the linear relationship between turbidity and sampling AD value.In the high turbidity range of 400-1000 NTU,it's the linear relationship of the approximate component segment between turbidity and sampling AD value.According to the actual measurement results,The photoelectric turbidimeter is designed by the international standard 90 degree scattering measurement method which has the advantages of high accuracy,low power consumption and good repeatability.,which meets all the technical paramaters in this paper.