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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: Density-independent microwave moisture sensing in flowing grain and seed

Authors
item Nelson, Stuart -
item Trabelsi, Samir
item Lewis, Micah

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 3, 2014
Publication Date: July 13, 2014
Citation: Nelson, S.O., Trabelsi, S., Lewis, M.A. 2014. Density-independent microwave moisture sensing in flowing grain and seed. ASABE Annual International Meeting. ASABE Paper No. 1895707.

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 grain and seed are highly correlated with the amount of moisture in these materials. Currently used techniques for rapid moisture measurement in grain and seed through sensing their dielectric properties require correction for density fluctuations in the grain and therefore are not suitable for reliable measurements on flowing grain because of unkown changes in the bulk density of grain as it flows. Sensing moisture content in grain and seed is possible by utilizing microwave frequencies and has been successfully demonstrated on static grain and seed samples. Although the theoretical basis for the density-independent grain moisture measurement is expected to be useful on flowing materials, successful use has not been demonstrated. A laboratory flowing grain system was built for tests of microwave moisture measurement that were conducted on shelled field corn, wheat, and soybeans. Appropriate software was written to control a microwave network analyzer for the necessary attenuation and phase measurements, and tests were run on flowing grain and seed materials of high and low moisture levels and at low, medium, and high flow rates. Results confirmed that moisture readings obtained on static and flowing grain and seed agreed well, demonstrating the usefulness of the microwave density-independent technique for monitoring moisture measurements on flowing grain. Such techniques for reliably measuring the moisture content of flowing grain may be useful on harvesting and processing equipment for grain and seed materials and provide improvement in efficiencies of managing such operations with benefits for producers, processors and consumers.

Technical Abstract: Current techniques for rapid moisture measurement in grain and seed through sensing the dielectric properties require correction for density fluctuations and therefore are not suitable for reliable measurements on flowing grain. Density-independent moisture sensing in grain and seed is possible at microwave frequencies and has been successfully demonstrated on static samples. Although the theoretical basis for the density-independent grain moisture measurement is expected to be useful on flowing materials, successful use had not been demonstrated. A laboratory flowing grain system was built for tests of microwave moisture measurement that were conducted on shelled field corn, wheat, and soybeans. Appropriate software was written to control a microwave network analyzer for the necessary attenuation and phase measurements, and tests were run on flowing grain and seed materials of high and low moisture levels and at low, medium, and high flow rates. Results confirmed that moisture readings obtained on static and flowing grain and seed agreed well, demonstrating the usefulness of the microwave density-independent technique for monitoring moisture measurements on flowing grain.

Last Modified: 12/24/2014
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