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Moisture Limits for Measurement of Moisture in Cereal Grains and Oilseeds Below Zero Degrees Celsius by the Dielectric Method

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  033020,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.15399)
Authors:   Péter Mészáros, David B. Funk
Keywords:   grain moisture, temperature correction, frozen grain, dielectric

Temperature profoundly affects the dielectric constant of moist materials--especially at the freezing point of water. For liquid water and moist materials that do not involve strong hydrogen bonding between water and the matrix, a dramatic discontinuity is observed in the dielectric constant versus temperature curve at zero degrees Celsius. Moisture measurements based on the radiofrequency dielectric method are essentially blind to "frozen" water. However, in materials such as grain where a significant fraction of the water is relatively tightly bound to polar molecules, this discontinuity is absent. The absence of that discontinuity in the dielectric characteristics of dry to moderately moist grains may permit accurate moisture measurements at temperatures well below the freezing point of water.

This research examined the low-temperature dielectric characteristics of several types of cereal grains and oilseeds to determine their high-moisture limits for measurements at temperatures below zero Celsius. These results are very important for the design of grain moisture meters to extend their useable temperature ranges below zero Celsius.

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