Development of moisture content sensor based on resonator

A coaxial resonator moisture content sensor is presented in this study based on the model of mixture dielectric characteristic. Then it figures out that the main factors influencing the moisture content measurement are the dielectric constant of protection cover and the no-load resonance frequency f_res . The comprehensive simulations are given to analyze the influences caused by two main factors in measurement. Three resonators with different operating frequencies and two protection covers made of distinct materials are presented. Experiments show that the methods adopted in the paper are constructive for designing sensors, also the no-load resonance frequency f_res should be near 2.5 GHz and the material of protection cover is Al₂O₃, to achieve good performances.