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ARS Home » Research » Publications at this Location » Publication #112648
Title: NEW CALIBRATION TECHNIQUE FOR MICROWAVE MOISTURE SENSORS

Author
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: 5/5/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Moisture content of cereal grains is a very important characteristic needed for determination of harvest time, selling price, suitability for storage, and proper condition for processing. Because of the correlation between moisture content and the electrical characteristics of grain known as dielectric properties, these properties can be sensed with electronic instruments operating at radio and microwave frequencies and calibrated to provide moisture content. At microwave frequencies, it has been shown that the dielectric properties can be used to provide reliable moisture contents independent of bulk density (packing) fluctuations in moving grain. New research has shown that use of a particular mathematical function of the dielectric properties can be used to provide reliable moisture contents of both wheat and corn over wide ranges of temperature and moisture content with the same calibration. This technique promises to provide a universal calibration for grain, which is an advantage over having to use different calibrations of moisture meters for each different kind of grain. It therefore offers an additional incentive for the development of practical grain moisture meters using this technique. Such instruments would provide the tools to improve both efficiencies in the handling and processing of grain and in the quality of end-use products for consumers.

Technical Abstract: A new calibration technique was developed for implementation in microwave moisture sensors. The calibration permittivity function used for this purpose allows computation of moisture content in granular materials with significant differences in shape, dimensions and composition independent of bulk density and with temperature compensation. A three-dimensional representation is used to plot the calibration permittivity function as it depends on temperature and moisture content in wheat and corn. For each material, data points form a plane surface. These planes have nearly the same coefficients which can be utilized for the development of a "universal" calibration method for moisture sensing in natural and manufactured granular materials. Foundations of the method are discussed, based on results obtained for wheat and corn over a wide temperature range and at moisture contents of practical interest.