ADVANCES IN SENSING GRAIN MOISTURE-CONTENT BY MICROWAVE MEASUREMENTS

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 a re presented, including techniques for moisture content determination independent of bulk density. Recent research findings on density-indep endent microwave determination of moisture content in grain are briefl y summarized Three functions of the grain dielectric properties or the wave parameters are identified from which moisture content can be det ermined independent of bulk density, and the performance of these dens ity-independent functions is compared for sensing moisture content in hard red winter wheat. Results show that standard errors of performanc e of about 0.3% moisture content or less can be achieved by using thes e functions with microwave measurements at frequencies between 11 and 18 GHz. Results of these and other cited studies indicate that measure ment techniques far density-independent moisture sensing in grain shou ld provide a sound basis for development of microwave moisture meters for on-line applications.