Research And Implementation Of PH Tester In Water Quality Detection

With the rapid development of the industry and increasing urban population, environmental issues have become a common concern. The key to environmental control is the analysis of water quality, while the most important of all is the control of the pH value of the surface water, thus it is in great urgency to design relevant measuring equipment. Owing the limited electronic technology and manufacturing technology, the domestic measuring technique of pH value is relatively backward with low automation. And thus it is of great significance to design a set of pH measuring equipment, which will be easy to carry with high accuracy and low cost.According to the need of practical application, the thesis has proposed a kind of pH measuring project based on the ADu CM360 micro processor, and it will be carried out from the two parts: the hardware circuit and the software program.The design of the hardware circuit mainly includes the following parts, namely, the power supply module circuit, signal conditioning circuit, A/D conversion module, temperature acquisition module, PWM temperature control module, isolated serial port communication module, and JTAG module. Taking ADu CM360 MCU as the core of the design, the voltage signal of the PT100 sensor will be collected as well as the amplified signal from pH electrode sensor, and then these signals will be transmitted to the ADu CM360 after A/D conversion. Finally the accurate pH value of the testing solution will be obtained through data processing, and it will be timely displayed on the PC after being transmitted by RS485.The software part can be divided into several programs, including pH value measuring program, temperature measuring program, A/D conversion subprogram, PID-PWM temperature control program, serial communication program, etc. Considering the effects of temperature on measuring results, the least squares algorithm is applied to the adjustment of program parameters to make linear compensation for the temperature of environment, which reduces the effects of the temperature change on measuring results. Besides, the two-point calibration method is employed to calibrate the tester, since it will age with the frequent use of the pH electrode. In short, all methods above have greatly increased the accuracy of the test pH tester, Therefore, this design has great significance on the research and innovation in the field of pH value test.