RF and Microwave Dielectric Properties of Shelled, Yellow-Dent Field Corn

THE dielectric properties of shelled corn were measured at frequencies of 20 MHz, 300 MHz, and 2.45 GHz as the corn dried from moisture contents as high as 40 percent to a low of about 10 percent. The dielectric constant was the most reliable dielectric property to use as an indicator of moisture content. Variability of the dielectric constant among 21 lots of corn was about the same at all three frequencies. Data are presented graphically showing the dependence of the dielectric pro-perties on moisture content, frequency, bulk density, and temperature. The dielectric constant increases with moisture content, bulk density, and temperature and decreases with frequency. The thermal coefficients and bulk density coefficients for the dielectric constant in-crease in magnitude with moisture content. Relation-ships are also shown between bulk and kernel densities and moisture content. Equations are presented for estimating the dielectric constant of shelled, yellow-dent field corn as a function of moisture content, bulk densi-ty, and temperature.