Determining physical properties of grain by microwave permittivity measurements
1999
Trabelsi, S. | Kraszewski, A.W. | Nelson, S.O.
Potential use of the complex permittivity measured at microwave frequencies for indirect nondestructive determination of physical properties of grain is discussed. Examples of extraction of bulk density and moisture content from permittivity measurements are shown for wheat and corn over wide ranges of frequency and temperature. Calibration equations for both entities are given along with their standard errors of performance (SEP). The bulk density of wheat and corn, ranging from 720 to 880 kg/m(3) and 695 to 830 kg/m(3), respectively, can be determined without prior knowledge of the sample moisture content or its temperature with, on average, SEP of 7.8 kg/m(3) and 12.9 kg/m(3), respectively. The moisture content of wheat and corn, ranging from 10.6 to 19.2% and 9.0 to 19.2%, wet basis, respectively, can be determined at a given temperature independent of density with SEP of less then 0.27% and 0.46%, respectively. One of the attractive features of permittivity-based methods is that they can be applied regardless of the measurement technique. One identified junction of the complex permittivity provides moisture content for both wheat and corn with the same calibration.
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