Moisture content measurement in the wood industry

Sammanfattning: In the wood industry, determination of the moisture content (mc) with a highaccuracy is of great importance. The green mc is important for optimisation of thewood drying process at sawmills, whereas the mc of dried boards is of interest for thefurther processing and final use of the boards. In the first publication in this thesis,which is a technical report written in Swedish, different measuring techniques withtheir own pros and cons are discussed. A total of 13 different measurement principlesare discussed, focusing on the ability to measure mc in the range of 7-18%. The resultsuggests that mc-meters that use electromagnetic waves in the radio- and microwaveranges have the greatest potential to become the next generation mc-meters for driedboards.The second publication, which is presented in this thesis, investigates the possibilityof measuring the green sapwood mc in pine logs by combining industrial X-rayscanners and 3D-scanners. The method is shown to be suitable for identifying batchesof logs in which the sapwood has begun to dry prior to sawing, rather than predictingthe sapwood mc with high accuracy at the level of individual logs.In a single board, one would ideally like to measure the mc profile over the entirecross section to determine the mc gradient. However, the measured result is affectedin the vicinity of the board edges. In the third publication, the existence of thisproblem is identified, and it is shown that it can be decreased by using correlationfunctions generated by finite element simulations of the measurement system.The fourth publication considers the potential to increase the measurement accuracyof the mc of single boards by combining different measurement techniques.Microwaves, X-rays and visual sorting into different wood quality classes are used. Itis shown that the measurement accuracy is increased by the addition of both the Xraymeasurements and the visual sorting. This result is interesting because visualsorting is usually already present in the final sorting of large sawmills. This is alsowhere the mc measurement preferably is to be performed.