The history of information development on the electrical properties of grain and their use for sensing moisture content is briefly reviewed. Basic principles of grain moisture sensing by microwave measurements are presented, including techniques formoisture content determination independent of bulk density. Recent research findings on density-independent microwave determination of moisture content in grain are briefly summarized. Three junctions of the grain dielectric properties or the waveparameters are identified from which moisture content can be determined independent of bulk density, and the performance of these density-independent junctions is compared for sensing moisture content in hard red winter wheat. Results show that standarderrors of performance of about 0.3 moisture content or less can be achieved by using these junctions with microwave measurements at frequencies between 11 and 18 GHz. Results of these and other cited studies indicate that measurement techniques fordensity-independent moisture sensing in grain should provide a sound basis for development of microwave moisture meters for on-line applications.
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