Frequency, moisture content, bulk density and hybrid effects on grain sorghum dielectric properties

Eros Estevão Moura, Pedro Amorim Berbert, Elias Fernandes Souza, Ricardo Ferreira Garcia, Marilia Amorim Molina, Marcia Ramos Oliveira


The interest in the dielectric properties of grains has been increasing over the years due to their potential utilization in advanced technologies such as the density-independent on-line estimation of moisture content in automatic control processes in grain drying operations. A capacitive sensor was used with a LCR meter to obtain a better understanding of the variation of relative permittivity and dielectric loss factor of four hybrids of grain sorghum in the frequency range from 75 kHz to 5 MHz, at 23°C and 62% relative humidity. Curves that are presented illustrate the variation of these dielectric properties on moisture content (7% to 23% w.b.), bulk density (575 to 819 kg/m3) and hybrid. The obtained results should provide a firm basis for future accurate, fast and non-destructive determination of grain moisture content and bulk density in automated industrial drying and storage processes.


relative permittivity, loss factor, radiofrequency impedance

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