Study On Non-contact Measurement Method And System For Water Conductivity

The conductivity was an important parameter of water electrical characteristics, it symbolized the strength of the conductive ability of water solution. However, the electromagnetic characteristics were important electrical characteristics of a conductive material, in the process of the change of conductive solution’s material components would have a obvious change. Magnetic induction measurement technology was based on the material of the different conductivity as the target conductor, measuring the phase change of the magnetic field before and after adding the target conductor, magnetic induction measurement technology was a detection principle of the size of the phase difference to explain the difference in electrical conductivity, in the measurement of non-contact with both avoiding the target water pollution, and reducing the error, but also making the magnetic induction measurement technology in industry, medical electronics industry and environmental monitoring field has been widely used.According to the eddy current measurement principle of magnetic induction characteristics, the thesis designed a set of non-contact magnetic induction water conductivity measurement system, excitation-detection coils measurement model was designed by the study of magnetic induction measurement technology; the excitation source of system has been designed with Arduino as its core processor, using digital frequency synthesis(DDS)technology to generate a sine wave, and after OPA603 amplifier and seven-order elliptic filter,to achieve signal generator of high stability, as the excitation source of system to drive the excitation coils; with Arduino as core processor of the phase detector, the phase detector was designed based on the phase detector chip AD8302, which could measure the phase difference between the detection signal and the reference signal; and using the front fully different filter based on LT6600 chip and the differential amplifier based on AD8130 chip dealt with the detection signal of system(filtering, amplification), to improve the reliability of the system;the human-computer interactive interface was designed by the serial port monitor of PC end and LCD, which would display magnetic induction signal detection data.The system’s main performance indicators were measured by the precision of phase detector and the phase resolution of water detection system as well as the conductivityresolution. The sodium chloride solution of different conductivity and water samples of different types were tested by this system, which obtained that different types of water solution have different phase difference, and the linear relationship between the conductivity of different water solution and phase difference. The experimental results demonstrated that the magnetic induction water conductivity measurement system could measure conductivity differences in the water sample, and could identify the categories of water, and the experimental results were consistent with magnetic induction detection principle.