Effect of Moisture Gradients on the Accuracy of Power-Loss Moisture Meters

Veneers of thickness approximately 0.10 inch, which had been equilibrated to known MCs, were stacked to form composite boards of thickness 1.5 inch, to simulate dimension lumber with moisture gradients. Comparisons were made between the true a average MCs (ovendry-weight method) and the MCs indicated by a power-loss-type meter. Results indicated that the presence of a moisture gradient, when the average MC exceeded 9 percent, caused the lower-loss meter to read lower than the true MC. This error can be very large. For example, in one test, while the true average MC was 102.2 percent, the meter indicated 16.9 percent. The cause of the errors is that the effective penetration of the electric field of this type of meter is not more than one-tenth of an inch.

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