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概要

Electro-Magnetic Induction Testing method is widely used in the industries. However, due to the deterioration of sensitivity by increase of Lift-Off (distance between sensor and test piece) and the limitation of penetration of magnetic flux into thick magnetic and conductive material such as carbon steel, its application is limited to comparative testing between sound and defective samples. The newly developed system enables the measurement of wall thickness and the detection of inner-surface defects even sensing from exterior of thermal insulator by applying FFT (Fast Fourier Transform) and digital processing in low- and multi-frequency range. Therefore, the system enables a screening inspection by the sensor placed exterior of the thermal insulator, and the precise measurement under the smaller Lift-Off after removal of the thermal insulator. The results are represented visually by 3D image. In addition, measuring technique in case of larger Lift-Off and larger wall thickness samples of non-magnetic material is also discussed..

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