RF Impedance and DC Conductance Determination of Moisture in Individual Soybeans

Abstract

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 moisture contents with a standard error of 0.68% moisture over measurements 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-diameter parallel-plate electrodes, produced moisture content determinations with a standard error of 0.56% moisture content. Thus, both techniques offer comparable accuracies when suitably calibrated.