An unilateral nuclear magnetic resonance (UMR) sensor was designed to measure wood moisture nondestructively. The sensor consisted of a unilateral magnet, an anti-eddy current module, a radiofrequency (RF) coil and an impedance matching and tuning circuit. The sensor produced a static magnetic field of 71.1 mT (resonant frequency:3.027 MHz) in a 50 mm×50 mm plane locating 75 mm above the sensor's surface. Preliminary nondestructive measurement of wood moisture was carried out with the sensor. The moisture distribution in the radical direction of a cylindrical wood sample was scanned. Variations in transverse relaxation time (T2) from the bark to core were obtained. Evaporation of moisture during wood drying was also measured with the UMR sensor. Experimental results showed that:the peak of long T2 component in the T2 spectrum moved to left and the peak integral area decreased gradually during drying. The integral area was proportional to the moisture content of the sample. The work presents a portable UMR device for wood research which may potentially be used for nondestructive moisture measurement on living trees in situ.
YU Deng-jie
,
GUO Pan
,
WU Jia-min
,
HE Yu-cheng
,
XU Zheng
. A Unilateral Nuclear Magnetic Resonance Sensor for Nondestructive Wood Moisture Measurements[J]. Chinese Journal of Magnetic Resonance, 2017
, 34(4)
: 508
-518
.
DOI: 10.11938/cjmr20172561
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