Applying the Correlation between Amplitude and Phase Change forMass-IndependentMoisture Content Evaluation of Wheat Flour

摘要

Nondestructive and mass-independent moisture content measurements are necessary for the quality control of wheat flours. Methods that use microwaves can evaluate the moisture content on both the surface layer and the inside of the bulk of the wheat flour. We describe the correlation between amplitude change at the resonance frequency and phase change at a specified frequency for varying masses of wheat flour, using a cylindrical cavity resonator operating at 3.920 GHz. Three types of wheat flours with moisture contents of 9.6, 13.2, and 16.6% were used up to 0.3 g in this experiment. The relation between the amplitude change at the resonance frequency and the phase change at the specified frequency was linear. The squares of the correlation coefficients of the linear approximation lines were both 0.999 for the three wheat flours. The three types of moisture contents were distinguished based on the difference in the slopes of the approximation lines. The validity of the experimental results was confirmed via calculations based on the S-parameter in the transmission characteristics of a two-port resonator. (c) 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.