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Microwave penetration in wood using imaging sensor
Luleå University of Technology, Division of Wood Technology, Skellefteå Campus.
2005 (English)In: Measurement, Vol. 38, 15-20 p.Article in journal (Refereed) Published
Abstract [en]

It is possible to determine properties of wood using microwave scanning techniques. The purpose of this study was to verify the measured values from a microwave imaging sensor. Attenuation and phase shift of an electromagnetic wave transmitted through birch wood were measured and compared with theoretical calculated values. A test piece with varying thickness was measured with a scanner based on a microwave sensor (Satimo 9.375 GHz) at different temperatures and moisture contents. The density distribution of the test piece was determined by computer tomography scanning. The result showed good correspondence between measured and theoretical values. The proportion of noise was higher at low moisture content due to lower attenuation. There is more noise in attenuation measurement than in measurement of phase shift. A reason for this could be that wood is an inhomogeneous material in which reflections and scattering affect attenuation more than phase shift. The microwave scanner has to be calibrated to a known dielectric to quantify the error in the measurement. (C) 2005 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
2005. Vol. 38, 15-20 p.
URN: urn:nbn:se:umu:diva-46077OAI: diva2:436949
Available from: 2011-08-25 Created: 2011-08-25 Last updated: 2011-09-07
In thesis
1. Microwave sensors for scanning of sawn timber
Open this publication in new window or tab >>Microwave sensors for scanning of sawn timber
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A microwave imaging sensor that measures the signal transmitted through a board was investigated with respect to the ability to predict the distribution of moisture and density in sawn lumber. Furthermore, the response from the sensor was related to strength properties of the boards. Multivariate statistics was used to relate the measured variables to various properties. A finite element model based on X-ray computed tomography images was developed to describe the interactions between microwaves and wood. The model made it possible to simulate the response from the sensor under varying conditions.

The results show that microwaves can be used for prediction of density and moisture content. They can also be used for prediction of strength properties, mainly from the correlation to density, but also from the influence on microwaves of structural variations in the wood. The finite element model is useful in the evaluation of microwave sensors for wood, drying equipment or other applications where electromagnetic waves interact with wood.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2007. 40 p.
, Doctoral thesis / Luleå University of Technology, 2007:9
microwave scanning; wood; density; moisture content; strength grading; finite element
National Category
Control Engineering
urn:nbn:se:umu:diva-46102 (URN)1402-1544 (ISBN)
Public defence
2007-04-18, Hörsal A, Forskargatan 1, Skellefteå, 10:00 (English)
Available from: 2011-08-29 Created: 2011-08-26 Last updated: 2011-08-29Bibliographically approved

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