Free-space measurement of dielectric properties of moist granular materials at microwave frequencies

Abstract

A-I: Calibration of dielectric-based sensors for reliable online moniforing and confrol of physical properties of moist granular materials requires accurate permittivity measuremenf. For this purpose, a free-space Iransmission fechnique, in which the main sources of errors were minimized, was used lo defermine the dielecfric properfies of three major commodities wheat, shelled corn and soybeans. Data collected at room temperature for different moisfure levels and wide bulk den@ ranges areprovided over a broad microwave frequency range. An erample of the use of dielectricproperfies for simultaneous moisture contenf and bulk density is given Dielecm‘c properties, adjusted for a medium density value through the use of the Landau and Lifshia, Looyenga dielectric mixture equation are listed for all three materials.