RF IMPEDANCE AND DC CONDUCTANCE DETERMINATION OF MOISTURE IN INDIVIDUAL SOYBEANS

Two electrical methods for determining the moisture content of single soybeans were compared to an oven drying reference method for moisture measurement. Moisture contents of the soybeans ranged from 7 to 20%, wet basis. A commercial instrument that measured the dc conductance of the soybeans as they passed between crushing-roller electrodes gave m oisture contents with a standard error of 0.68% moisture over measurem ents on soybeans of four cultivars from soybean producing areas in the Midwest and the Southeast. Capacitance measurements at 1 and 5 MHz on the same single soybeans, held between and in contact with 2-cm-diame ter parallel-plate electrodes, produced moisture content determination s with a standard error of 0.56% moisture content. Thus, both techniqu es offer comparable accuracies when suitably calibrated.