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United States Department of Agriculture

Agricultural Research Service

Research Project: SENSING METHODS & INSTRUMENTATION FOR RAPID DETERMINATION OF MOISTURE CONTENT... AND OTHER QUALITY ATTRIBUTES OF GRAINS, SEEDS, & NUTS

Location: Quality and Safety Assessment Research Unit

Title: Microwave moisture sensing through use of a piecewise density-independent function

Authors
item Mckeown, Murat -
item Trabelsi, Samir
item Tollner, Ernest -

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 6, 2013
Publication Date: May 6, 2013
Citation: Mckeown, M.S., Trabelsi, S., Tollner, E.W. 2013. Microwave moisture sensing through use of a piecewise density-independent function. Proceedings of the 2013 International Instrumentation and Measurement Technology Conference. p.1712-1716.

Interpretive Summary: Dielectric properties of materials are electrical properties that determine how materials interact with electric fields such as those of high-frequency and microwave electromagnetic energy. Dielectric properties of agricultural products are useful in rapidly measuring moisture content, since the dielectric properties of water are much greater than those of the other constituents. Microwave moisture sensing provides a means to determine nondestructively the amount of water in such materials. This is accomplished through the correlation of dielectric properties with moisture in the material. In this study, linear relationships between a density-independent function of the dielectric properties and moisture content of minced Vidalia onions were identified. It was observed that two straight lines with a slope change at 40% moisture content, could represent the dielectric constant of onion tissue between 6% and 92% moisture content. Similarly the dielectric loss factor could be represented with two straight lines with slope dependent on moisture range. Utilizing a function of the dielectric constant and loss factor, which is known to be independent of the bulk density of the minced onions, a two-slope (piecewise) linear regression of that function and moisture content provided useful relationships for predicting moisture content from the measured dielectric properties of the minced onions over the complete moisture range, 6% to 92%. Results showed the prediction of moisture content with a coefficient of determination of 0.976. The measurements and techniques presented in this study constitute a foundation for the development of a moisture sensor that would be useful for growers and processors, and result in improved quality for consumers.

Technical Abstract: Microwave moisture sensing provides a means to determine nondestructively the amount of water in materials. This is accomplished through the correlation of dielectric properties with moisture in the material. In this study, linear relationships between a density-independent function of the dielectric properties and moisture content of minced Vidalia onions, with slope dependent on moisture range, is identified. This allows prediction of moisture contents between 6% and 92%. Results showed the prediction of moisture content with a coefficient of determination of 0.976. The measurements and techniques presented in this study constitute a foundation for the development of a stand-alone sensor.

Last Modified: 12/19/2014
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