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United States Department of Agriculture

Agricultural Research Service


item Trabelsi, Samir
item Kraszewski, Andrzej
item Nelson, Stuart

Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Proceedings
Publication Acceptance Date: 8/30/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: There is a need in modern agriculture for sensors that can determine important characteristics of agricultural products on-line, i.e., while they are being harvested, marketed, and transported for processing or storage. For grain and seed crops, their moisture content is one of the most important characteristics, because it determines their safe storage potential and is important in determining the market price. The bulk density of materials is also an important factor. Test weight of grains is a bulk density measurement under defined conditions. Because it is an important quality factor it is also important in determining the selling price. Microwave measurements of the dielectric properties of grain and seed materials have been found to be useful in determining both moisture content and bulk density. Studies are described in this paper which demonstrate a new technique for determining both moisture content and bulk density of wheat, oats, and soybeans, based on the microwave dielectric properties of these materials, which can be sensed on-line by appropriate electronics equipment. In addition, the technique provides a single calibration equation for moisture determination that can be used for all three different commodities with good accuracy. This finding should help to provide an incentive for development of microwave moisture and bulk density sensing equipment that would be useful in determining and preserving the quality of these agricultural products.

Technical Abstract: A microwave method for determining bulk density and moisture content in cereal grains and seed from measurement of their dielectric properties at a single frequency is presented. Bulk density is determined from a complex-plane representation of the dielectric properties normalized to density without knowledge of the moisture content and temperature of the sample material. The moisture content is determined with a permittivity-based calibration function that increases linearly with moisture content. Bulk density and moisture calibration equations are given for wheat, oats, and soybeans along with the standard error of calibration for each material. Because the calibration function used for moisture prediction is independent of both bulk density and the kind of material, a unified moisture calibration is established for all three materials.

Last Modified: 08/21/2017
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