Measurement of the capacitance and conductance of a capacitor filled with samples of wheat allows the determination of two dielectric properties of the material: the relative permissivity (epsilon'), and the dielectric loss factor (epsilon"). The use of these two properties, measured simultaneously at two different frequencies of the electric field, permits bulk density-independent measurement of moisture content of wheat. This procedure makes it possible to monitor moisture content continuously, and on-line, of a moving column of grain, a situation where the greatest variations in bulk density are to be expected. The objective of the present research was the derivation of density-independent equations for the determination of moisture content of wheat. Samples of varieties Hussar, Mercia and Hereward at moisture contents ranging from 11% to 22% w.b., and bulk densities ranging from 666 to 873 kg m-3 have been used. The best-performance equation was capable of estimating moisture content of wheat with standard errors of calibration and prediction of 0.4 and 0.5 percentage point moisture, respectively.
capacitance; dielectric properties; instrumentation
