Author
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NELSON, STUART |
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Submitted to: IEEE Transactions on Dielectrics and electrical Insulation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/21/2005 Publication Date: 8/15/2006 Citation: Nelson, S.O. 2006. Agricultural Applications of Dielectric Measurements. IEEE Transactions on Dielectrics and Electricl Insulation. Volume 13(4):Page No. 688-702. Interpretive Summary: Dielectric properties of materials are electrical properties that determine how materials interact with electric fields such as those of high-frequency and microwave electromagnetic energy. Therefore, the dielectric properties of materials determine how rapidly they will heat in microwave ovens and lower radio-frequency dielectric heating equipment. Dielectric properties are also important in low power applications, such as the rapid measurement of moisture content in grain and other commodities. Electronic moisture meters use radio-frequency electric fields to sense moisture content in products such as grain, because the dielectric properties are highly correlated with the moisture content of the grain. This review paper describes those applications of dielectric properties in the agricultural area, providing some history of the interest in dielectric properties of grain and seed. It reviews the techniques used over wide ranges of frequency for the measurement of dielectric properties of grain, insects, fruits, and vegetables and presents dielectric properties data for these materials and describes the application of dielectric properties information for a few uses in agriculture. These applications include moisture measurement in grain, possible control of stored-grain insects through selective dielectric heating of the insects, and possible use of dielectric properties for sensing of maturity in fruits and vegetables. The mathematical relationships between dielectric properties of granular and powdered materials and their bulk densities are also discussed because of their importance in reliably using the dielectric properties of grain and other such particulate materials. The information presented may interest engineers in developing instruments that could provide important tools for improving agricultural production, product maintenance and quality preservation, and marketing for the benefit of growers, processors and consumers. Technical Abstract: 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. |
