Abstract：A dual-frequency resonant sensor is designed based on the interdigital capacitance structure to measure the complex permittivity of liquid. The advantages of the sensor in sensitivity, miniaturization and operating bandwidth are verified by simulation analysis, machining and measurement. The results of simulation and measurement show that the sensitivity of the dual-band resonant sensor is as high as 5.2%, which can realize the nondestructive measurement of the complex permittivity of the liquid at two frequency points with a very small amount of liquid at the same time, and can measure the concentration of methanol-ethanol mixed solution based on certain calibration operations. The measurement error of liquid complex permittivity is reduced from 4.2% to 2% by obtaining the test data of two frequency points simultaneously. In addition, the structure size of the interdigital capacitor can be further adjusted to develop a multi-band resonant sensor to achieve accurate acquisition of the wide-band dielectric spectrum of the liquid.
2024, Vol. 45 
