WOOD RESEARCH Volume 61, Number 1, 2016
Katarzyna Pentoś, Deta Łuczycka, and Tobiasz Wysoczański

The use of complex impedance as a parameter for wood differentiation

Electrical and dielectric wood properties are used in many applications. Wood parameters such as resistance, conductivity, complex impedance can be used e.g. for determination fungal decay, moisture content and density or for defects detection. In this work, the complex impedance of seven wood species was measured for frequency range 10 Hz – 1 MHz. The specimens were cut from sapwood and heartwood and measurements were conducted with parallel and perpendicular orientation of the electrical field with respect to the visible grain. The impedance of various wood types differs significantly for frequencies below 2 kHz. Therefore, for wood samples classification, the complex impedance values measured in frequency 1.1 kHz were used. Three different classification methods were used for clustering. Results show that the impedance can be a useful parameter for wood differentiation and membership of each group depends on number of clusters.

WOOD RESEARCH Volume 62, Number 5, 2017
Katarzyna Pentoś, Deta Łuczycka, and Tobiasz Wysoczański

Dielectric properties of selected wood species in Poland

The dielectric properties of seven wood species from Poland were measured as a function of frequency and grain orientation of wood. Measurements were conducted parallel and perpendicular with respect to the visible grain for specimen cut from sapwood and heartwood, at frequencies ranging from 1 kHz to 1 MHz. Both, relative permittivity and loss coefficient were affected by frequency and anisotropic direction. The most significant influence of wood species on dielectric wood properties was observed below 5 kHz for relative permittivity and below 200 kHz for loss coefficient. The relative permittivity decreases with increasing frequency and loss coefficient increases with increasing frequency (at frequencies above 200 kHz) for all wood species and fiber orientation. Understanding the dependencies between dielectric parameters of wood and other wood parameters at frequency range from 1 kHz to 1 MHz is important when wood is used for electrical insulation or in high-frequency drying.