| 摘要 |
PURPOSE:To accomplish a sensitivity calibration automatically and quickly corresponding to various outer diameters simply by preparing a comparison test piece of the min. outer diameter, by employing a gain correction circuit to enable a sensitivity calibration applying the outer diameter of the comparison test piece in combination with the outer diameter of material to be inspected. CONSTITUTION:A slide magnetic pole 2 is combined slidably with a fixed magnetic pole 1 to be moved forward and backward in the opposite direction to each other through a screw shaft 4. The magnetic pole 2 is provided with a magnetizing coil 5 to magnetize material 6 to be inspected placed in a clearance between the magnetic poles. Then, first, a plurality of samples of varied diameters which was made of the same material as the comparison test piece for calibration and given an artificial flaw is used to obtain a characteristic curve for a flaw signal detection voltage. Then, flaw signal voltages V3 and V4 are determined based on the characteristic curve with respect to the outer diameter phi3 of the comparison test piece and the outer diameter phi4 of the material being inspected and a sensitivity calibration is performed using the value of the ratio V3/V4 as correction value. This correction value is automatically set with a gain correction circuit. |
