Unilateral magnetic resonance spot estimates of bulk moisture conte

In this study, spot measurements of bulk moisture content (MC) in black spruce were determined by unilateral magnetic resonance (UMR). The unilateral magnet employed has a region of homogenous magnetic field, located approximately 1.3 cm away from the top surface of the magnet. The RF coil in combination with the static topology gives a sensitive spot of approximately 1 cm³. This is significant because we can now measure signal within a finite volume inside the sample and through the bark. The goal of this study is to locate the best possible place to make spot MC measurements in wood log. Wood log comprises primarily of sapwood and heartwood. In the case of the species studied, there is a significant difference in moisture content between sapwood and heartwood regions. The sapwood region contained approximately 3 times more water than heartwood. However, the volume of heartwood is greater than sapwood in wood logs. This is the reason a line integrating measurement such as Ground Penetrating Radar is problematic. The sapwood region contains most of the water; therefore a measurement in the sapwood coupled with sapwood to heartwood volume ratio will be a better approach in estimating bulk MC of logs. Correct bulk MC estimates of logs will help wood manufacturers alleviate product quality problems and improve process efficiency.

Preliminary results indicate that the best spot to make MC measurements of logs after 30 days of air drying is a few centimeters (approximately 15 cm) from the ends. The end surfaces dry faster than wood inside the log therefore end measurements will be problematic. Spatially resolved imaging measurements were employed to verify the UMR results.