Patent ID: 7705589
Filing Date: 2010-04-27
Classification: G01N

Abstract:
1. A sensor for detecting surface defects of a metal tube, the sensor comprising a plurality of coils wound at a predetermined inclined angle, wherein the plurality of coils is inserted into the inside of a metal tube and an alternating current is applied to the coils to measure a change in impedance of the coils due to a change in an eddy current generated in the metal tube, thus detecting a surface defect of the metal tube, wherein the plurality of coils performs the roles of an exciting coil for generating an eddy current and a sensing coil for detecting the change in the impedance of the coils at the same time so as to detect a defect using a principle that a balance of a voltage induced in one coil and a voltage induced in the other coil is broken when the defect passes through one of the coils.