2.Experiment to measure the excitation current value when obtaining magnetic particle indication
Fig. 1 shows the configuration of the type A standard test shims used in this work. They consisted of an iron sheet having soft magnetic properties with a thickness of 50 or 100 mm. An iron sheet in the as-rolled condition has been used for the type A2 standard test shim. An iron sheet annealed at 600 C for 1 hand furnace cooled has been used for the type A1 standard test shim. The type A standard test shim had a 20 mm × 20 mm area with a 6 mm long artificial groove at the center. Shape of the artificial groove was either circular or linear. The circular groove has been