Wood Moisture Gradient Analysis by Electrical Impedance Spectroscopy

An electrical impedance frequency spectrum (20Hz to 1 MHz) was measured in wood specimens with uniform, absorption and desorption transverse moisture content (MC) gradient. Parallel plate single sided capacitive and conductive electrodes were used. Capacitance, conductance and impedance locus analyses were included in the study, the desorption and absorption moisture gradients (MG) were estimated using frequency based analysis. This study suggests that the transverse MG can be estimated using impedance spectroscopy analysis. Both used electrode types and all the studied methods gave similar results which shows that frequency based analysis can be used. It was not possible to achieve very good accuracy when estimating MG using pure conductive or capacitance measurement method. The electrical distributed network circuit modelling was found to be the most promising method in estimation of transverse MG.