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United States Department of Agriculture

Agricultural Research Service

Title: A Microwave Method for on-Line Determination of Bulk Density and Moisture Content of Particulate Materials

Authors
item Trabelsi, Samir - OICD
item Kraszewski, Andrzej
item Nelson, Stuart

Submitted to: Institute of Electrical and Electronics Engineers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 8, 1998
Publication Date: N/A

Interpretive Summary: Moisture content of grain and other particulate agricultural materials is a vital factor in determining the length of time they can be stored without spoilage. Therefore the ability to monitor moisture content accurately in flowing grain and other products, from harvest through marketing, transportation and processing, would be very useful in maintaining high quality. The electrical or dielectric properties of such products are highly correlated with moisture content, and, therefore, suitable electronic instruments can be used for moisture measurement. However, with granular materials, fluctuations in the packing, or bulk density, of such products make reliable moisture measurement very difficult. In research on electronic techniques for sensing moisture content, a new mathematical function has been developed which has a very fundamental physical basis that is described in the article. An application is described for which the use of the new function provides accurate moisture contents for sample of wheat at various moisture contents, temperatures and bulk densities. The bulk density of the grain is also provided by the same data and also provides the value of the bulk density. The new mathematical function has wider applicability than previously developed functions, and should provide advantages in accurately monitoring grain moisture content to improve quality of grain and grain products for domestic use and for export.

Technical Abstract: A new method for simultaneous on-line determination of bulk density and moisture content in particulate materials by measurements of the complex permittivity is proposed. The bulk density is determined, based on a representation in the complex plane of relative complex permittivity normalized to bulk density. For moisture content determination, a new density-independent function, exclusively dependent on dielectric properties, is used. Results obtained from measurements on wheat over broad ranges of microwave frequencies, temperatures, densities and moisture contents are presented.

Last Modified: 11/24/2014
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