Abstract:In view of the traditional water quality detection,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.The conductivity measurement equipment is not only suitable for the measurement of low conductivity in actual production applications,but also needs to take into account the measurement of high conductivity,and the demand for conductivity measurement accuracy is getting higher and higher.In this paper,a high-precision self-calibration range adaptive conductivity detection circuit is designed for the above problems.The excitation signal with conductivity information and the reference excitation signal without the conductivity cell are cross-correlated by the circuit and filtered by the low-pass filter to obtain the voltage signal related to the conductivity.The sine 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.The range switching circuit ensures the wide range of conductivity measurement.The cross-correlation algorithm is used to reduce the circuit noise and remove the equivalent capacitance of the conductivity cell,which makes up for the shortcomings of the traditional conductivity measurement circuit,such as quantitative range,small measurement range and poor accuracy.The test results show that the conductivity measurement circuit can measure the conductivity range of 0~30000 pS/cm,the measurement accuracy of 0.01 μS/cm,and the measurement baseline noise of 0.3 nS/cm.