Dielectric Permittivity Measurement Based on Input Impedance Variations

This paper presents a non-destructive method for measuring the permittivity of a relatively large dielectric material, based on the variation in the input impedance of a probe touching the surface of the material. In this work a wire dipole has been found suitable to be used as the probe. The method requires a theoretical model describing the variation of the resonance frequency of the dipole situated at the interface of a dielectric half-space. The model has been developed in this work using the method of moments. Dielectric permittivity is measured by placing the dipole on the surface of the material and by measuring the first resonance frequency in the input impedance of the dipole. The measured frequency is then compared with the theoretical model to determine the dielectric permittivity of the material. Measurement using another method which is more straightforward has been carried out to validate the proposed method. Good agreement between both methods has been observed.