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Principles for Microwave Sensing of Moisture Content in Grain

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  026008,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.10544) @2002
Authors:   Stuart O. Nelson, Samir Trabelsi
Keywords:   Microwave measurements, Grain moisture, Moisture sensing, Permitivity, Dielectric properties

The importance of cereal grain moisture content in determining time of harvest and in preserving grain quality is described. Techniques for moisture measurement, including electronic moisture meters, are also discussed briefly, and the need for better moisture sensing techniques for modern agricultural on-line moisture monitoring is described. Principles of microwave freespace measurements involving attenuation and phase determination are explained, and densityindependent functions of the grain permittivity are presented that permit reliable moisture sensing applicable to moving grain in which bulk density variation occurs. A new moisture calibration function, based on complex-plane plots of dielectric constant and loss factor, each divided by bulk density, is described, which promises a universal calibration for different types of grain and seed. This important advantage should encourage commercial development for practical use.

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