A capacitive multi-wavelength sensor for moisture content gradient sensing in wood
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Technical advancements in the field of capacitive sensing and the availability of multi-channel capacitance-to-digital converters have led the way for improved sensing capabilities in the field of wood moisture content. A four-channel, planar capacitance sensor was developed and calibrated on maple veneers. The calibration material was conditioned to equilibrium at three different relative humidity levels. Optimal penetration depths were determined statistically and analytically. A rule of mixture approach and a volumetric model were applied to derive the moisture content at distinct layers. Different levels of discrepancy of the fit were observed among and within the different electrodes and calibration datasets. The sensor was able to determine changes in moisture content and positive moisture content gradients, rather than averages, with the limitation of detecting negative moisture gradients.
This work was supported and funded through the National Science Foundation Industry/University Cooperative Research Center for Wood Based Composites award no. IIP-1624599. A special thanks goes to Milo Clauson, Senior Research Assistant in the Department of Wood Science and Engineering at Oregon State University, for his help and advice.
- Forsén H, Tarvainen V (2000) Accuracy and functionality of hand held wood moisture content meters. Technical Research Centre of Finland Espoo, FinlandGoogle Scholar
- Fuchs A, Moser MJ, Zangl H, Bretterklieber T (2009) Using capacitive sensing to determine the moisture content of wood pellets–investigations and application. Int J Smart Sens Intell Syst 2:293–308Google Scholar
- Ihaka R, Gentleman R (1996) R: a language for data analysis and graphics. J Comput Graph Stat 5:299–314Google Scholar
- James WL (1963) Electric moisture meters for wood. Department of Agriculture, Forest Service, Forest Products Laboratory, MadisonGoogle Scholar
- James WL (1975) Dielectric properties of wood and hardboard: variation with temperature, frequency, moisture content, and grain orientation (No. FSRP-FPL-245). Forest Products Lab MadisonGoogle Scholar
- James WL (1986) The interaction of electrode design and moisture gradients in dielectric measurements on wood. Wood Fiber Sci Number 2:264–275Google Scholar
- Jazayeri S, Ahmet K (2000) Detection of transverse moisture gradients in timber by measurements of capacitance using a multiple-electrode arrangement. For Prod J 50:27–32Google Scholar
- Li X, Zyuzin AS, Mamishev AV (2003) Measuring moisture content in cookies using dielectric spectroscopy. In: Conference on electrical insulation and dielectric phenomena, 2003. Annual report. IEEE, pp 459–62Google Scholar
- Torgovnikov GI (1993) Dielectric Properties of Wood-Based Materials. Springer, Berlin, pp 135–159Google Scholar