High-frequency densitometry - a new method for the rapic evaluation of-wood density variations

摘要

A new method called HF-densitometry is introduced, which measures relative density variations along wood surfaces utilizing the dielectric properties of wood. The method is based on the propagation of continuous electromagnetic waves in a high-frequency (HF) transmitter-receiver link of an extremely small electrode system, which is in direct contact with the wood surface investigated. The electromagnetic field emitted by the transmitting electrode propagates through a small volume of the wood sample to the receiving electrode, located very close to the transmitting electrode. The received signal strength is directly influenced by the dielectric properties of the material along the propagation path. The variation of the relative dielectric constant in different wood structures is correlated with the density variations in a way the received signal strength increases with increasing wood density. The dielectric measuring device, developed on the basis of the new method, allows non-destructive, extremely fast measurements of wood density variations. The new HF-densitometry method was compared to X-ray densitometry by performing measurements on an identical spruce sample.