Abstract:In view of the traditional water quality testing, agricultural irrigation, metal material process control and emerging wine identification, salt content detection, drug extraction and other new problems, the requirements for conductivity measurement accuracy and measurement range are constantly improving, requiring conductivity measurement equipment not only suitable for low conductivity measurement in practical production applications, but also need to take into account high conductivity measurement, and the demand for conductivity measurement accuracy is getting higher and higher. In this paper, a high-precision self-calibrating range adaptive conductivity detection circuit is designed, through which the excitation signal with conductivity information is cross-correlated with the reference excitation signal of the unpassed conductivity cell, and the conductivity-related voltage signal is obtained by filtering it by the low-pass filter. The sinusoidal excitation amplitude adjustable circuit and the automatic calibration module in the conductivity measurement circuit cooperate with each other to complete the automatic calibration of the circuit, and the range switching circuit ensures the wide range of conductivity measurement, making up for the shortcomings of the traditional conductivity measurement circuit of quantitative range, small measurement range and poor accuracy. The test results show that the conductivity measurement circuit can measure the conductivity range of 0-30000uS/cm, the measurement accuracy is 0.01uS/cm, and the measurement baseline noise is 0.3ns/cm.