Wood moisture content measurement at 2.45 GHz

Wood, being one of the most widely used construction materials by industry, relies on its moisture content for strength, durability and ductility. Lumber industry has long been searching for a non-destructive, accurate and fast method to determine moisture content in wood to replace the traditional one based on weighing. This paper evaluates the performance of a 2.45 GHz measuring system that determines moisture content of 4 cm thick wood samples. If dry wood and water densities are defined as the ratio between their masses and the volume of the wood sample, then they can be estimated by establishing the attenuation, phase shift and depolarization of the electromagnetic wave that propagates through the wood. Using this technique, moisture content of Radiata pine tree boards in the range of 0 to 68% has been established, with dry wood density ranging from 390 to 530 Kg/m³ and water density from 0 to 285 Kg/m3. This is an improvement of 2.4 times of previously reported measurements.