Submitted to: Journal of Microwave Power and Electromagnetic Energy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/1996
Publication Date: N/A
Interpretive Summary: Most grain moisture meters used by farmers, grain elevator operators, and others throughout the grain industry use the electrical characteristics of grain, known as dielectric properties, for the instantaneous sensing of moisture content. While the dielectric properties are correlated with moisture content, they are also influenced by the test weight, or bulk density, of the grain. Most grain moisture meters use radio frequencies below the microwave range for sensing the moisture content of grain samples. Moisture sensing techniques that use microwaves can determine moisture content independent of density variations. These microwave measurement techniques should make it possible to monitor moisture content in grain that is being conveyed through chutes or on belts and thus provide a continuous record of moisture content in grain lots as they are being transferred. This paper reports results of careful measurements of the microwave dielectric properties of shelled, yellow-dent field corn that will be helpful in determining characteristics of grain moisture monitoring systems based on microwave characteristics. The final results will permit design of monitoring systems that will be helpful in maintaining high quality grain products for domestic and export uses.
Technical Abstract: Dielectric properties of three hybrids of shelled, yellow-dent field corn were measured at different bulk densities and moisture contents in a Styrofoam container located between two horn antennas in free space. Relative complex permittivities were determined from measurements of attenuation and phase shift at frequencies from 11 to 18 GHz and at temperatures from 4 to 45 deg C. The grain moisture content ranged from about 9% to 19%, wet basis.