Author
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Nelson, Stuart |
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Submitted to: ASAE Annual International Meeting
Publication Type: Other Publication Acceptance Date: 4/18/2005 Publication Date: 7/17/2005 Citation: Nelson, S.O. 2005. Dielectric properties measurement for agricultural applications. In: Proceedings of the American Society of Agricultural Engineers, St. Joseph, MI. Paper No. 053134. 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 some of 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 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 grain, insects, and fruit 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 also discussed for the use of microwave dielectric properties for sensing moisture content in grain. |
