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Title: DIELECTRIC METHODS FOR MULTIPARAMETER MICROWAVE SENSOR

Author
item TRABELSI, SAMIR - UNIV GEORGIA
item Nelson, Stuart

Submitted to: Electromagnetic Wave Interaction with Water and Moist Substances Proceeding
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2003
Publication Date: 3/25/2003
Citation: TRABELSI, S., NELSON, S.O. DIELECTRIC METHODS FOR MULTIPARAMETER MICROWAVE SENSOR. PROCEEDINGS OF THE 5TH INTERNATIONAL ELECTROMAGNETIC WAVE INTERACTION WITH WATER AND MOIST SUBSTANCES, ROTORUA, NEW ZEALAND. 2003. p. 56-63.

Interpretive Summary: There is a need for more reliable rapid moisture content sensing in agricultural products such as grain and seed so that farmers and grain and oilseed handlers can prevent spoilage when moisture content is too high and better manage operations for maintenance of high quality in such commodities. New microwave measurement techniques offer promise for improving the sensing of moisture and other physical characteristics of grain and seed such as bulk density. The microwave techniques for sensing moisture content and bulk density of grain and seed are described in this paper. They require the determination of the electrical characteristics of the grain and seed known as dielectric properties. When these dielectric properties are measured at microwave frequencies, they can then be used to calculate the moisture content and the bulk density of the material. Because the dielectric properties also depend on temperature as well as upon moisture content and bulk density, the relationships of the dielectric properties with temperature of the grain and seed must also be determined. Then calibration equations can be developed to provide moisture content and bulk density directly from the dielectric properties data. Results reported in this paper reveal that a single calibration equation serves to provide moisture content for corn, wheat, and soybeans, whereas separate calibration equations have always been required for each different kind of grain or seed with existing moisture meters. Thus, it should be possible to develop a microwave moisture meter with a universal calibration for granular materials that will provide reliable moisture content information, which will benefit farmers, and processors and provide improved products for the consumer.

Technical Abstract: Three dielectric-based approaches are presented for predicting physical properties of grain and seed from measurement of their dielectric properties. In the first approach, regression analysis provided explicit direct relationships between the dielectric properties of these materials and their physical properties, i. e., bulk density, moisture content, and temperature. In the second approach, the complex-plane representation provides an expression for bulk density in terms of the dielectric properties that is independent of moisture content and temperature. In the third approach, a single permittivity-based moisture calibration equation is used to determine moisture content in granular materials presenting significant structural and compositional differences. All of these approaches and relationships established in this study may constitute the basis for development of dielectric-based multiparameter sensors for indirect, nondestructive, and instantaneous determination of physical properties of granular materials from measurement of their dielectric properties.