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Title: DENSITY-INDEPENDENT FUNCTIONS FOR ON-LINE MICROWAVE MOISTURE METERS: A GENERAL DISCUSSION

Author
item TRABELSI, SAMIR - OICD
item NELSON, STUART

Submitted to: Measurement Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Better methods are needed for monitoring the moisture content of grain to provide better information for quality management from harvesting through storage, transport and processing. For many years the electrical characteristics of cereal grains, known as dielectric properties, have been used by electronic moisture meters for rapid moisture testing of grain samples. Adequate sampling is always a problem to be dealt with. Microwave measurements that sense the dielectric properties, which are highly correlated with moisture content, offer an opportunity for the development of instruments that can continuously monitor the moisture content of moving grain for on-line moisture information. The fluctuation in the packing, or bulk density, of grain as it moves through conveyors produces significant errors in moisture measurement. This paper presents results of a study on the effectiveness of three different methods for moisture content determinations by microwave measurements on wheat. The systematic analysis revealed that by use of appropriate density-independent functions that can be incorporated into the calibration equations for microwave moisture meters, the errors associated with density fluctuations in moving grain can be practically eliminated. These findings should aid the development of practical reliable microwave moisture monitors for application in grain production, handling, and processing, with improvement in the quality of American grain for domestic use and for export.

Technical Abstract: Density-independent calibration functions are a suitable solution for bulk density variation problems in on-line determination of moisture content in particulate materials by microwave techniques. Foundations of three of these functions are briefly reviewed and their frequency and temperature behavior are shown for wheat. Their effectiveness for moisture content prediction is compared, and optimum conditions for a cost-effective moisture meter are discussed.