Detection of transverse moisture gradients in timber by measurements ofcapacitance using a multiple-electrode arrangement

摘要

Current commercial dielectric hand-held timber moisture meters provide no means of identifying transverse moisture gradients. This paper presents the results of a study into the detection of transverse moisture gradients in timber using a method of precision capacitance measurement at a frequency of 1 MHz. Measurements were carried out using a multiple-planar-electrode arrangement on stacked veneer samples where systematic moisture gradients were introduced. Results from utilizing various configurations of live electrodes show that although the scanning depth is affected by the moisture profile, a consistent increase is observed in the effective penetration depth of the electromagnetic waves as electrode separation is increased, yielding accurate moisture profiles to moderate depths.