The Design And Technology Research On TDS Measurement Instrument For Drinking Water

With the improvement of living standard, people are increasingly concerned about the problem of drinking water quality. For drinking water quality, we can use three parameters as a measure of standard, namely: TDS, residual chlorine, p H value. TDS is an important factor affecting the quality of drinking water, it will directly affect the taste of water. So, it is more important to measure the value of TDS in real time and more accurately.TDS is abbreviation of the total dissolved solids, which is obtained by measuring the electrical conductivity of the water. With the development of microprocessor technology and integrated circuit technology, the measurement method of electrode type conductivity has become the most popular method. The bridge method, differential pressure method, phase sensitive demodulation method, frequency method had made full use of the microprocessor's powerful processing capability and rich resources, and can achieve the temperature automatic compensation function, the measurement accuracy has been greatly improved.On the basis of a large number of domestic and foreign references, this paper analyzes the advantages and disadvantages of the commonly used methods of electrical conductivity measurement, and summarizes the influence factors on the accuracy of electrode type conductivity measurement, which are the influence of the polarization effect of the electrodes, the effect of the electric conductivity pool, the water temperature. Based on it, this paper use the dual frequency sinusoidal measurement method and introduces the measuring principle, and through formula deduction to explain them. Using the STM32 microprocessor chip as the core to complete the relevant circuit design, mainly include sinusoidal signal generator circuit, temperature measurement and compensation circuit, communication interface circuit and display module design. STM32 controls AD9851 to generate two different frequency sine wave; with DS18B20 to achieve temperature acquisition, and then through the programming to realize the automatic temperature compensation; STM32 controls the LCD driver chip ILI9341 to realize the real-time display of the detection data, the communication interface designs RS-485 interface and Ethernet interface, through the transplantation of TCP/IP protocol stack to achieve network communication. There are two ways to achieve the server design, respectively, Cloud server design and the Internet configuration software Web Access design.