A dual-parameters microwave measurement approach for spruce moisture content

Moisture content (MC) serves as a pivotal metric for assessing the wood quality, impacting crucial properties such as density, stiffness, and strength. Accurate determination of MC is imperative for ensuring quality and meeting specifications. This study introduces a novel dual-parameters microwave measurement methodology designed for precise MC quantification in spruce. By analyzing the sensitivity and linearity of the S21 with MC across both the S and X bands, we identify the most effective measurement parameters. Experimental work further investigates the correlation between the amplitude and phase of S21 and the MC in spruce, laying the groundwork for a comprehensive understanding of moisture influence on wood properties through microwave techniques. Finally, considering the impact of MC on both the amplitude and phase of S21, we introduce a dual-parameters microwave approach for accurately determining spruce MC. This method has been validated through case studies in both X and S bands. Our discussion extends to the effects of wood material characteristics, moisture distribution within samples, wood texture directions, and specimen dimensions on S21. Experimental results confirm that this approach significantly improves the precision of MC measurements in spruce, achieving an error rate of 0.15% in X band and 0.49% in S band measurements.