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ARS Home » Research » Publications at this Location » Publication #96272
Title: DETERMINING PHYSICAL PROPERTIES OF GRAIN BY MICROWAVE PERMITTIVITY MEASUREMENTS

Author
item TRABELSI, SAMIR - OICD
item KRASZEWSKI, ANDRZEJ
item NELSON, STUART

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Moisture content of grain is very important in determining safe storage conditions for grain to prevent spoilage. Therefore, moisture content must be measured at harvest and whenever grain is sold. The price is affected by moisture content, not only because the costs for drying must be considered, but also because the water in the grain has less value than the grain dry matter. Since the permittivity, or dielectric properties (electrical characteristics), of grain are highly correlated with its moisture content, electronic grain moisture testers have been developed that provide quick moisture tests. However, samples from grain lots must be taken judiciously and then tested to obtain reliable moisture information on the whole grain lot. Recent research has shown that microwave measurements should be useful for monitoring moisture in flowing or moving grain and that the grain bulk density can also be sensed with the same measurements. The microwave measurements and use of the permittivity for determining moisture content of wheat and corn are described, and accuracies better than of 0.3 percent moisture content for wheat and 0.5 percent moisture content for corn were achieved. One calibration was found suitable for both kinds of grain. The techniques, when implemented for on-line grain moisture monitoring, can provide information to system managers for preserving grain quality and improving quality in processed grain products which will help to maintain the competitive advantage of American producers in the global market.

Technical Abstract: Potential use of the complex permittivity measured at microwave frequencies for indirect nondestructive determination of physical properties of grain is discussed. Examples of extraction of bulk density and moisture content from permittivity measurements are shown for wheat and corn over wide ranges of frequency and temperature. Calibration equations for both entities are given along with their standard errors of performance. One o the attractive features of permittivity-based methods is that they can be applied regardless of the measurement technique. One identified function of the complex permittivity provides moisture content for both wheat and corn with the same calibration.