ADVANCES IN SENSING GRAIN MOISTURE CONTENT BY MICROWAVE MEASUREMENTS

Abstract

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 for moisture content determination independent of bulk density. Recent research findings on densityindependent microwave determination of moisture content in grain are briefly summarized. Three functions of the grain dielectric properties or the wave parameters are identified from which moisture content can be determined independent of bulk density, and the performance of these density-independent functions is compared for sensing moisture content in hard red winter wheat. Results show that standard errors of performance of about 0.3% moisture content or less can be achieved by using these functions with microwave measurements at frequencies between 11 and 18 GHz. Results of these and other cited studies indicate that measurement techniques for density-independent moisture sensing in grain should provide a sound basis for development of microwave moisture meters for on-line applications.