Design of a Trace Moisture Content Detection System Based on Microfluidic Chip

Since the traditional coulomb method has the disadvantages such as time-consuming, waste liquid pollution when detecting the water content in transformer oil, explore new detection method to replace traditional coulomb method is extremely urgent. According to the principle that the dielectric constant of polymer film changes with the changes of environmental relative humidity, polymer capacitive humidity sensor can reflect the trace moisture content in the samples by the changes of capacitance, which has the advantages of high speed, high precision. In this paper, combining microfluidic chip technology with polymer capacitive humidity sensor, a new microfluidic chip is designed to detect the trace moisture content in transformer oil. Since the structures of test oil channel and standard oil channel in the chip are completely symmetrical, small capacitance can be converted into voltage signal which is easy to measure and acquire by amplification and conversion of capacitance signal. And the voltage differential signal from Capacitance/Voltage(C/V) conversion circuit can effectively reduce the measuring error due to parasitic capacitance. The number of electrodes in standard oil channel and test oil channel can be set different by controlling the valves in the chip, which will realize the amplification of the detection signal and expanding the range of detection. This detection chip has the advantages of simple structure, convenient operation, multi-mode measurement and high sensitivity. It has a broad application prospect in the field of trace moisture detection.