An eddy current test system is described in which the test information is detected as a series of fields reflected from the metal surface and interior. Pulsed electromagnetic fields are caused to impinge upon the test specimen. These fields are restricted to a small cross sectional area over a path in space long enough to be useful for test purposes by devices called mask-apenture assemblies. This approach provides a number of advantages over conventional eddy current methods of comparable capabilities, including superior surface resolution, a reduction in circuit complexity, and an improvement in stability and reliability. Various applications and test results are discussed. (auth)