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Methods of Controlling Lift - off in Conductivity Invariance Phenomenon for Eddy Current Testing
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  • Zhongwen Jin ,
  • Yuwei Meng ,
  • Rongdong Yu ,
  • Ruochen Huang ,
  • Mingyang Lu ,
  • Hanyang Xu ,
  • Xiaobai Meng ,
  • Qian Zhao ,
  • zhijie zhang ,
  • anthony peyton ,
  • wuliang yin
Zhongwen Jin
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Yuwei Meng
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Rongdong Yu
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Ruochen Huang
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Mingyang Lu
University of Manchester

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Hanyang Xu
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Xiaobai Meng
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Qian Zhao
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zhijie zhang
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anthony peyton
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wuliang yin
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Previously, a conductivity invariance phenomena (CIP) has been discovered – at a certain lift-off, the inductance change of the sensor due to a test sample is immune to conductivity variations, i.e. the inductance – lift-off curve passes through a common point at a certain lift-off, termed as conductivity invariance lift-off. However, this conductivity invariance lift-off is fixed for a particular sensor setup, which is not convenient for various sample conditions. In this paper, we propose using two parameters in the coil design – the horizontal and vertical distances between the transmitter and the receiver to control the conductivity invariance lift-off. The relationship between these two parameters and the conductivity invariance lift-off is investigated by simulation and experiments and it has been found that there is an approximate linear relationship between these two parameters and the conductivity invariance lift-off. This is useful for applications where the measurements have restrictions on lift-off, e.g. uneven coating thickness which limits the range of the lift-off of probe during the measurements. Therefore, based on this relationship, it can be easier to adjust the configuration of the probe for a better inspection of the test samples.
2020Published in IEEE Access volume 8 on pages 122413-122421. 10.1109/ACCESS.2020.3007216