SENSITIVITY CALIBRATION METHOD FOR MAGNETIC FLAW DETECTION DEVICE

PURPOSE:To easily and accurately calibrate sensitivity when a thin sheet steel is fed by providing a magnetism sensing element group, a frequency filter, and an absolute value circuit. CONSTITUTION:A detection head 2 is equipped with a fluid flotation type follow-up mechanism which incorporates the magnetism sensing element group 1 on the top surface side of a material S to be inspected. Then when the material S to be inspected is magnetized by an electromagnet 3, leak magnetism of intensity proportional to the surface roughness of the material S to be inspected is generated. Further, the leak magnetism detected by the element group 1 is converted into an electric signal, which is amplified 4 and passed through the frequency filter 5 to remove its noises. Then the signal passing through the filter 5 enters the absolute value circuit 7 through an attenuator 6 to obtain the absolute value of the signal voltage. A sample holding circuit 8 at a following stage samples the input signal for a constant time to hold the peak value within the sampling time and the peak value is read in a computer 9 the sampling time later.