A Cavity Perturbation Method for Routine Permittivity Measurement^*

Abstract

A novel method of permittivity measurement by a cavity perturbation technique at microwave frequencies is suggested. The method employs a frequency counter for the determination of a cavity Q factor instead of a rather sophisticated circuitry previously used.The principle of operation, uncertainty analysis and measurement set up are described. The structure of the resonator and the sample holder permit continuous control and monitoring of a sample temperature. The method was verified experimentally by measuring a few substances of known permittivities. Dielectric properties of several foodstuffs measured using this method are reported.Both the analysis and the experiment showed that the accuracy of the method is comparable with that of the most accurate methods employing frequency markers while the measurement procedure is simpler and the equipment needed is usually easily available.