Electrical conductivity measurement method in seawater desalination based on variable frequency excitation

Abstract

Electrical conductivity is one of the necessary parameters of water quality detection in the seawater desalination. By analyzing the shortcomings of traditional measurement methods, an electrical conductivity measurement method based on the variable frequency excitation was proposed. The factors affecting measurement error such as temperature, electrode polarization and capacitance effect were analyzed. It was demonstrated that the variable frequency excitation method can effectively overcome the error caused by these factors. Sine wave with different frequency was taken as excitation source for different electrical conductivity range. The appropriate feedback resistor was selected in the measurement circuit. The electrical conductivity signal was obtained by the exact signal amplifier circuit and acquisition circuit. The measurement value was obtained after temperature compensation. The measurement system was calibrated with conductivity calibration solution. Finally the accurate value can be got. This method meets the accuracy requirement of online water quality monitoring in seawater desalination.