Microwave Resonator Technique for Moisture Content Determination in Single Soybean Seeds

A rectangular waveguide cavity operating in the H107 mode at 6.0 GHz was used to measure the resonant frequency Shift and the change in 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 those two parameters and the amount of water in the seeds and their dry mass. Moisture content, being a ratio of these two masses, may therefore be expressed in terms of two measured cavity parameters, regardless of the size of the seed. With this technique, the moisture content of soybeans, Glycine max L., in the range from 7 to 16 percent can be determined with an uncertainty of 0.9 percent at the 95-percent confidence level.