JPS57146158A - Eddy current flaw detecting device - Google Patents

Abstract

PURPOSE:To set the direction of noise component for every material to be checked automatically, by utilizing the fact that the number of signals caused by the flaw among the signals outputted during the flaw detection in the continuous casting and the like is very small, extracting a constant number of outputs in a time series, and determining appropriate polar coordinate rotary angle. CONSTITUTION:The output signals of a detector 2, which is generated by the distribution of the eddy current caused in the material to be checked 5, are given to phase discriminators 4a and 4b. Component signals X and Y which cross to each other are obtained. Said signals X and Y are outputted to a computing and processing part 7. When the flaw detection has started, the polar coordinate rotary angle H is initially set at zero. When X and Y are inputted to a point N, linear approximation of the set is performed based on the information at the point N, while Y'=(tantheta)X' is obtained, and compensated rotary angle theta is obtained. Said compensated angle theta is added to H and H'=H+theta is used as an optimum polar coordinate rotary angle. Then the operation of the polar coordinate rotation is performed to obtain X' and Y', and they are displayed on a display part 10. In this constitution, even through the direction of the signal other than the flaw is changed, the optimum polar coordinate rotation can be readily performed.