Universal calibration for microwave moisture sensors for granular materials

A universal calibration method for microwave moisture sensors for granular materials is presented. The method is based on measurement of the dielectric properties and the use of a complex-plane representation of the normalized complex permittivity. Effectiveness of this method in moisture content prediction is tested for granular materials presenting significant structural and compositional differences. A single moisture calibration equation is given at 9.46 GHz and 24/spl deg/C for wheat, oats and soybeans.