Effect of soft rot and bacteria on electrical impedance of wood at low moisture content

A complex nonlinear-modelling-based electrical impedance spectroscopy (EIS) for the analysis of decay (soft rot and bacteria) in wood was introduced. Small wood specimens (5 x 10 x 100 mm) including three degrees of decay (control and two decay conditions) were measured by impedance spectroscopy at frequencies between 80 Hz and 1 MHz. The effect of decay on impedance was studied by EIS-modelling and constant frequency parameter analysis at two different moisture content levels below fibre saturation point. Two ZC-circuits in series were used in modelling. The distribution parameter v(1) of the double ZC-model decreased with increasing decay, the reduced values of the distribution parameter were affected by the increased variability in the wood cell structure. The effect of decay on constant frequency parameters was neglible compared to the moisture content effect. Thus, it was possible to estimate both decay condition and moisture content level of each specimen by combined method of EIS-modelling and constant frequency parameter analysis.