Density-independent high moisture content measurement using phase shifts at two microwave frequencies.

Density-independent high moisture content measurement is required in actual production line. In this paper, the experimental results for high moisture content measurement using microwave free-space technique are presented. The method is based on a ratio of phase shifts at two microwave frequencies after propagating through a sample. The experiments were performed with three kinds of sawdust named Momizai, Cedar and Douglas Fir. In the high moisture content above 130%, the root mean square error (RMSE) of moisture determination by the method for three kinds of sawdust are 9.0%, 17.0%, 22.8%, respectively.