Design And Realization Of Optical Turbidity Sensor

The turbidity of water is caused by suspended matter such as silt, clay, fine organic matter and inorganic matter, plankton and other microorganisms. The impurity particles can become the carrier of bacteria and viruses and parcel layer, reduce the chloride ion, UV and ozone disinfection antiseptic effect of water, may lead to the spread of disease. And in some industrial production process, the turbidity directly affect the product quality. Therefore, the water turbidity of on-line detection has very important practical significance.Since the measurement methods of 90° scattering and the surface scattering only have high precision in the low or high turbidity range, a new type of turbidity detection structure with 45 degree angle is proposed and designed. A new type of turbidity detector integrating the two measurement methods is designed, which can effectively broaden the turbidity measurement range and reduce the system volume and cost. In the hardware design, mainly to complete the drive comprises a light source, extract weak signal amplification, A/D sampling, serial communication circuit. In the experiment, when a beam of parallel light is launched into the solution under test, two photodetectors are used to detect the 90° scattering light and the surface scattering light simultaneously. According to the technique characteristics of the two methods, when the turbidity measurement result lies in 0-300NTU or >300NTU, the raw data obtained from the 90° scattering method or the surface scattering method is chosen for processing and analyzing, respectively. Our experimental results show that the turbidity sensor can precisely measure the turbidity of the solution in a wide range of 0-4000NTU with the measure accuracy less than ±5%F.S. In the experimental temperature and stability test, the turbidity sensor also showed good stability. In summary the developed turbidity sensor has advantages of litlle power consumption, wide detection range, low cost, which may find profound applications in the fields of environmental monitoring, wastewater treatment, etc.