Attenuation-only Method for Moisture Sensing in Granular Materials

A method for nondestructive moisture content determination in granular materials from measurement of attenuation only at microwave frequencies is proposed. For purpose of illustration, the measurements were carried out on wheat, corn, and soybeans at room temperature (23 °C) for frequencies ranging from 7 GHz to 12 GHz with a free-space transmission technique. Linear correlations between attenuation and moisture content provided moisture content were identified. For each material and each frequency moisture content calibration equations were established. At each frequency, performance of these equations in moisture prediction from attenuation measurement were evaluated by calculating the standard error of calibration (SEC). Values of the SEC ranged from 0.34% to 1.45%.