Research of Possibilities to Test Wood Humidity and Density by Non-Destructive Capacitance Technique

Testing of wood humidity directly in a product or in wood processing conveyers is an actual problem. The only acceptable techniques at present are indirect methods based on measurement of correlated physical properties, particularly wood dielectric parameters. These techniques provide possibility to apply laid-on or built in the test piece sensors comprising several electrically charged electrodes. However, significant disturbing factors take place as the dielectric properties of these sensors depends not only from humidity of the test piece, but also of the wood species and structure (density, porosity). Conventional testing facilities observe influence of the wood species by visual monitoring and introduction of relevant corrections in the test result. Research and development of possibilities for physical determination of the wood species in order to introduce corrections in the measurement result of moisture testing is the main goal of the present work. The main conclusion of this work is that the measurement of the dielectric permeability at various frequencies provides possibility to determine indirectly humidity and density satisfactorily selective. There are obtained curves for a few species of wood by HP4194A Impedance/Gain-Phase Analyzer and by computer program GRAFQWIN: density and humidity error dependences from a wood humidity standard valu