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ARS Home » Research » Publications at this Location » Publication #114251
Title: UNIVERSAL MICROWAVE MOISTURE SENSOR FOR GRANULAR MATERIALS

Author
item TRABELSI, SAMIR - OICD
item Kraszewski, Andrzej
item Nelson, Stuart

Submitted to: Transactions of the ASAE
Publication Type: Proceedings
Publication Acceptance Date: 7/25/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Moisture content of cereal grains and oilseed crops is a very important characteristic needed for determination of harvest time, selling price, suitability for storage, and proper condition for processing. Because of the correlation between moisture content and the electrical characteristics known as dielectric properties, these properties can be sensed with electronic instruments operating at radio and microwave frequencies and calibrated to provide moisture content. At microwave frequencies, it has been shown that the dielectric properties can be used to provide reliable moisture contents independent of bulk density (packing) fluctuations in moving grain. New research has shown that use of a particular mathematical function of the dielectric properties can be used to provide reliable moisture contents of wheat, oats, and soybeans over wide ranges of moisture content and bulk density with the same calibration. This technique promises to provide a universal calibration for grain and oilseeds, which is an advantage over the current need for different calibrations of moisture meters for each commodity. Thus, it offers an additional incentive for the development of practical grain moisture meters using this technique. Such instruments would provide the tools to improve both efficiencies in the handling and processing of grain and oilseeds and in the quality of end-use products for consumers.

Technical Abstract: A feasibility study of a universal calibration for nondestructive real-time microwave sensing of moisture content in granular materials is described. The principle is based on measurement of the dielectric properties of grains at microwave frequencies and the use of a calibration function that is expressed in terms of these properties to predict moisture content in those grains from a single moisture calibration equation. Effectiveness o this method is shown for three granular materials exhibiting significant structural and compositional differences: wheat, oats and soybeans. The resulting single moisture calibration equation, based on measurements of the dielectric properties at 9.4 GHz and 24 degrees C, provides moisture content in all three materials with a standard error of calibration of 0.46% moisture content, wet basis.