A Unilateral Nuclear Magnetic Resonance Sensor for Nondestructive Wood Moisture Measurements

doi:10.11938/cjmr20172561

Abstract

Abstract: 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.

Key words: unilateral nuclear magnetic resonance (UMR), sensor, wood, moisture, non-destructive detection

CLC Number:

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.

References

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