Microwave resonator technique for moisture content determination in single soybean seeds

A rectangular waveguide cavity in the H₁₀₅ and H₁₀₇ modes at 4.8 and 6.0 GHz, respectively, was used to measure the resonant frequency shift and the change in the Q-factor caused by seeds of various dimensions and different hydration levels, located in the center of the cavity. Significant statistical correlations were found between measured parameters and the amount of water in the seeds and their dry mass. An empirical approach consists of relating the ratio of these two cavity parameters with the seed moisture content by a curve fitting method. With either of these techniques, the moisture content of soybeans, Glycine max L., in the range from 7 to 16% can be determined with an uncertainty lower than 1% at the 95% confidence level