Microwave moisture measurement of grains

Abstract

A two-parameter transmission technique is described for online, in situ measurement of the bulk moisture content of grains using microwaves. This noncontacting 4.9-GHz system is configured so that a well-collimated TEM beam is transmitted through a layer of grain, e.g., moving on a conveyer or flowing in a chute. The changes in attenuation and phase serve as two independent measurement parameters from which the wet and dry basis weights (grams per square centimeter) and moisture can be found using a linear model, independent of the layer thickness. If the layer thickness is also known, the wet and dry densities (grams per cubic centimeter) and complex dielectric constant can be found.