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Title: MICROWAVE DIELECTRIC METHODS FOR SENSING PHYSICAL PROPERTIES OF GRANULAR MATERIALS

Author
item TRABELSI, SAMIR - UNIV OF GA-ATHENS,GA USA
item Nelson, Stuart

Submitted to: National Radio Science Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/15/2002
Publication Date: 7/15/2002
Citation: TRABELSI, S., NELSON, S.O. MICROWAVE DIELECTRIC METHODS FOR SENSING PHYSICAL PROPERTIES OF GRANULAR MATERIALS. 2002 USNC/URSI NATIONAL RADIO SCIENCE MEETING DIGEST. 2002. P. 155.

Interpretive Summary:

Technical Abstract: Knowledge of the physical properties of granular materials is important in many industries including food and agriculture, pharmaceutical, chemical, and mining. They are often used in quality control as well as process monitoring and control. Therefore, they need to be determined reliably and in real time to meet requirements and standards of highly automated industries. Dielectric-based sensors can provide an adequate solution for such challenges. Unlike traditional measurement methods that necessitate off-line testing of samples requiring some time, dielectric-based sensors rely on indirect determination of the desired property from measurement of the dielectric properties characterizing the electromagnetic wave/material interaction. These sensors can be used for continuous, nondestructive assessment of the physical properties of all the processed material. The dielectric properties of granular materials such as cereal grain and seed are known to be dependent upon frequency, temperature, bulk density, moisture content and composition. Therefore, they cannot be used directly to predict one or more physical properties without compensating for or eliminating the effects of the remaining factors influencing the measured dielectric properties. In this presentation, microwave dielectric methods are developed for simultaneous and independent determination of bulk density (r), moisture content (?), water partial bulk density (mw/v) and dry matter partial bulk density (md/v). These methods are based on a complex-plane representation of the complex permittivity for bulk density determination (S. Trabelsi et al., Meas. Sci. Technol., 12, 2192-2197, 2001), and on permittivity calibration functions for moisture sensing independent of bulk density changes (S. Trabelsi and S. O. Nelson, Meas. Sci. Technol., 9, 570-578, 1998). Some new empirical relations are given for determining partial densities. Also the foundation of a universal algorithm that remains valid across moisture sensors of different designs is presented. Finally, incentives and challenges for implementation of these methods in the design of versatile and cost-effective microwave sensors are discussed.