Title: Density-Permittivity Relationships for Powdered and Granular Materials Author
Submitted to: IEEE Transactions on Instrumentation and Measurement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 28, 2004
Publication Date: October 3, 2005
Citation: Nelson, S.O. 2005. Density-permittivity relationships for powdered and granular materials. IEEE Transactions on Instrumentation and Measurement. 54(5):2003-2040 Technical Abstract: The dielectric properties of cereal grains and oilseeds are used in the determination of moisture content by electrical and electronic moisture meters. The dielectric properties of materials are those electrical characteristics that determine the interaction of the material and electric fields that can be used to sense moisture content instantaneously in properly designed moisture meters. However, the packing, or bulk density, of such granular materials interferes with accurate moisture measurement if differences in packing are not taken into account. This paper provides a detailed discussion of the influence of bulk density on the dielectric properties of powdered and granular materials. It also summarizes results of research to define relationships between the dielectric properties and the bulk density of such materials as wheat, wheat flour, and pulverized coal, limestone, and some plastics. A recommended equation for correcting the dielectric properties for changes in the bulk density of such materials is presented. This information will be useful to those designing moisture meters for grain and seed and other granular or pulverized materials to provide more reliable moisture information for the management of grain and seed harvesting, storage, marketing and processing operations. Consequently, maintenance of better quality in agricultural grain and oilseed crops and products from those crops will benefit both producers and consumers.