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Title: CALIBRATION METHODS FOR NONDESTRUCTIVE MICROWAVE SENSING OF MOISTURE CONTENT AND BULK DENSITY OF GRANULAR MATERIALS

Author
item TRABELSI, SAMIR - UNIV OF GEORGIA
item Nelson, Stuart

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2004
Publication Date: 12/22/2004
Citation: Trabelsi, S., Nelson, S.O. 2004. Calibration methods for nondestructive microwave sensing of moisture content and bulk density of granular materials. Transactions of the ASAE. 47(6):1999-2008.

Interpretive Summary: There is a need for moisture sensors for grain and seed that can provide reliable information on-line in harvesting, transfer, and processing of these commodities. Good information on moisture content is necessary for yield monitoring on combines in precision agriculture applications, and reliable moisture information is needed as grain is traded and transferred into storage. Recent research has shown that microwave measurements can provide such information, and research is continuing on development of basic information upon which design of microwave sensors can be based. This paper discusses the principles for nondestructive simultaneous sensing of moisture content and bulk density (packing density) of grain and seed. Different approaches are presented for the calibration of microwave sensors based on these principles. The subsequent development of practical microwave sensors for moisture and density will provide managers with new tools for rapidly determining quality of agricultural products and providing high quality grain and seed products for consumers and for the export market.

Technical Abstract: The principles of a nondestructive multiparameter microwave sensor operating at a single frequency are presented. Three methods of calibration are investigated for simultaneous, independent determination of bulk density and moisture content in granular materials. The first calibration method is based on measured attenuation and phase shift through a layer of material in free space. In the second calibration method, relationships are established between the complex permittivity and bulk density and moisture content. In the third method, functions of the complex permittivity are correlated to moisture content and bulk density. The second and third calibration methods are permittivity-based and thus can be used regardless of the measurement technique. Performance of these calibration methods is tested for wheat, corn and soybeans at 10.0 GHz at room temperature. Method 3 presents the most attractive features for implementation in a cost-effective microwave multiparameter sensor.