Agricultural applications of dielectric measurements

A brief historical perspective on dielectric properties of agricultural products is presented, including their use for rapid measurement of moisture content in grain and in considering potential dielectric heating applications. General principles are discussed as they relate to dielectric properties of materials and energy absorption from radio-frequency and microwave electric fields. Measurement principles and techniques for determining the dielectric properties of agricultural materials are described, and appropriate references are cited for detailed information. Dielectric properties data for some grain, insects, fruits, and vegetables are presented that relate to applications for selective heating of insects in grain and potential maturity and quality sensing in fresh fruits and vegetables. Principles are discussed for the use of microwave dielectric properties for sensing moisture content in grain, and relationships between dielectric properties of granular and powdered materials and their bulk densities are described