In order to solve the problem that the water film and salt scale on the inner wall of the resonant cavity sensor could reduce the accuracy measurement of the wetness

a method for measuring the dielectric film thickness on the inner wall of cylindrical cavity is proposed in this paper. Based on the principle of dielectric perturbation method

this method uses the hyperbolic cosine-shaped slot resonator as a sensor

working at the TE

111

mode to measure the dielectric film thickness. Taking the water film as an example

the relationship between the water film thickness and the resonant frequency is deduced theoretically

and the feasibility of measuring the water film by TE

111

mode is analyzed through simulation. We establish the mathematical model of the current density distribution line of the cavity end face for the TE

111

mode by the method of vector field equation

and design the hyperbolic cosine-shaped slot resonator sensor. The simulation results show that the performances of the electromagnetic characteristics

radiation characteristics and flow characteristics of the resonator are all relatively well. The electromagnetic leakage rate is basically 0

and the sampling error is-1.25%

which meet the design requirements. The water film thickness

salt scale

oil film

fouling and other dielectric films can be measured accurately. It is also shown that the film thickness is linearly related to the resonance frequency offset

which are consistent with the theory.