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    Author(s): W. L. James; Y.-H. Yen; R. J. King
    Date: 1985
    Source: (Research note FPL ; 0250):9 p. ; 28 cm.
    Publication Series: Research Note (RN)
    Station: Forest Products Laboratory
    PDF: View PDF  (125 KB)

    Description

    The attenuation, phase shift and depolarization of a polarized 4.81-gigahertz wave as it is transmitted through a wood specimen can provide estimates of the moisture content (MC), density, and grain angle of the specimen. Calibrations are empirical, and computations are complicated, with considerable interaction between parameters. Measured dielectric parameters, however, correlate uniquely and repeatably with MC over a range of MC at least as great as 100 percent of the dry weight of the wood. Grain angle can be deduced reliably when the specimen thickness and MC are great enough to introduce sufficient dielectric anisotropy to appreciably depolarize the incident wave. At present, the apparatus and techniques are very complex, but the principles developed by this research show the method to be feasible for nondestructive testing of lumber as it is produced.

    Publication Notes

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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    James, W. L.; Yen, Y.-H.; King, R. J. 1985. A microwave method for measuring moisture content, density, and grain angle of wood. (Research note FPL ; 0250):9 p. ; 28 cm.

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    Keywords

    Microwaves, Dielectric properties, Non-destructive testing, Moisture content, Density, Attenuation, Grain and figure, Wood density, Wood moisture, Phase shift, Depolarization, Homodyne

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