Calibrating free-space measurement systems for microwave moisture sensing in granular materials

The universal character of a permittivity-based calibration function for moisture determination in granular materials such as cereal grain and seed is tested through measurement at microwave frequencies on materials of different structure and composition using two free-space measurement arrangements. Results obtained from measurements on wheat, corn and soybeans provide moisture calibration equations with temperature compensation that are very similar for both systems leading to a single moisture calibration equation and the potential of transferability of the calibration routine across instruments of different designs.