ARS | Publication request: UNIFIED ALGORITHM FOR MICROWAVE SENSING OF MOISTURE IN GRAIN AND SEED

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: May 20, 2006
Publication Date: July 9, 2006
Citation: Trabelsi, S., Nelson, S.O. 2006. Unified algorithm for microwave sensing of moisture in grain and seed. American Society of Agricultural and Biological Engineers Paper Series. Paper number 063094.

Interpretive Summary: The electrical characteristics of grain known as dielectric properties are used by electronic grain moisture meters for rapid determination of moisture content. Moisture content is important in determining the potential for safe storage of grain, and it must be measured whenever a grain lot is sold. Recent research has shown that measurements on grain at microwave frequencies offer advantages for moisture testing compared to the lower radio frequencies currently used by commercial grain moisture meters. This research has also shown that the moisture content of grain can be rapidly obtained from microwave measurements that determine the dielectric propertiesof the grain independent of fluctuations in the bulk density (packing) of the grain, which causes errors in the moisture content indicated by currently used moisture meters if it is not taken into account. Therefore the microwave sensing of grain moisture content shows promise for on-line monitoring of moisture in grain and seed. New research with samples of corn, wheat, barley, grain sorghum, and soybeans has shown that moisture content of any of these commodities can be sensed at microwave frequencies with a single calibration, whereas separate calibrations are currently required for each different kind of grain. The new information is useful to engineers developing new moisture meters and it will therefore contribute to the goal of providing high quality and healthful products for consumers.

Technical Abstract: A unified calibration algorithm for moisture sensing in grain and seed from a single calibration equation, which is obtained from measurement of their dielectric properties at a single microwave frequency is presented. This algorithm is based on a calibration function that is expressed in terms of the dielectric properties. It is independent of both bulk density changes and the kind of material. Performance of the unified algorithm was tested for soybeans, corn, wheat, sorghum and barley at 7 GHz and about 23 degrees Celsius. The standard error of calibration for moisture prediction from dielectric properties measurement was 0.8%.