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Title: DENSITY-INDEPENDENT AND TEMPERATURE-COMPENSATED MICROWAVE DIELECTRIC METHOD FOR MOISTURE SENSING IN GRAIN AND SEED

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

Submitted to: Agricultural Engineering International Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/29/2002
Publication Date: 7/29/2002
Citation: TRABELSI, S., NELSON, S.O. DENSITY-INDEPENDENT AND TEMPERATURE-COMPENSATED MICROWAVE DIELECTRIC METHOD FOR MOISTURE SENSING IN GRAIN AND SEED. AGRICULTURAL ENGINEERING INTERNATIONAL CONFERENCE PROCEEDINGS, CHICAGO, ILLINOIS. PAPER NO. 023069. 2002.

Interpretive Summary: Because grain and seed moisture content is such an important factor determining time for harvest, selling price, suitability for storage or transport, and conditioning required for optimum processing, new and improved methods are needed for rapidly sensing the moisture content of grain and oilseeds. Research has shown that moisture content can be sensed through the electrical characteristics of grain and seed known as dielectric properties. There are some important advantages of sensing moisture content at microwave frequencies rather than the lower frequencies currently used for grain moisture meters. This paper describes some of these advantages and provides new evidence that moisture content can be determined rapidly from measurement of the dielectric properties of the grain or seed by two different techniques with similar results. In both methods, the dielectric properties were sensed with antennas and laboratory measurement instruments. Using this technique, moisture content is calculated from the dielectric properties of the grain without any need for information on the bulk density of the grain or its temperature. The method also offers promise for a universal calibration for grain and seed, so that separate calibrations for different kinds of grain and seed are unnecessary. The advantages of the microwave technique should find interest among instrument manufacturers in developing microwave moisture meters for use in the grain and seed trade.

Technical Abstract: A Microwave dielectric method is presented for sensing moisture in grain and seed independent of bulk density and with temperature compensation. The method is based on the use of a moisture calibration function that is defined in terms of the measured dielectric properties. A three-dimensional representation of the calibration function as a function of moisture content and temperature was used to generate moisture calibration equations for wheat, corn and soybeans. For each material, results from measurements with two different free-space arrangements at 7.0 GHz and 14.2 GHz show that all the data points form a plane surface in three dimensions with data corresponding to different temperatures forming a network of parallel lines. The regression coefficients for all three materials are nearly the same, even though these granular materials are different in shape, dimensions, and composition, and the measurements were carried out with two different measurement setups. The independence of the permitivity-based moisture calibration function from the kind of grain or the measuring instruments provides a universal moisture calibration for granular materials. Thus, it may be used for moisture sensing in different granular materials with instrumentation of different designs.