Electrical Moisture Meter Readings on Western Hemlock Dimension Lumber

Fifty pieces of 2-inch western hemlock (Tsuga heterophylla (Raf.) Sarg.) dimension lumber were measured for moisture content with a radio-frequency power loss meter and a resistance meter, then by ovendrying. The moisture content determined by ovendrying averaged 16.0 percent; the power-loss meter averaged 18.8 percent; the resistance meter (1/5 the board thickness) averaged 15.0 percent; and the resistance meter in the core averaged 16.6 percent. The average specific gravity was 0.46. Samples with specific gravities of 0.50 or more generally caused readings of the power-loss meter to be higher than actual average moisture content. The resistance meter readings were not affected by specific gravity. Both meter readings were higher than the actual average moisture content when the measurement was made in an area containing a wet pocket. Linear regression analysis was applied to determine the relations of the power-loss and resistance meter readings (1/5 the board thickness) to the actual average moisture content of each specimen. In the analysis of power-loss meter readings, the correlation coefficient was 0.78, and the correlation coefficient for resistance meter readings was 0.82. The test of linearity for both regressions tested not significant at the 5 percent level of probability.

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