Alternating current field measurement (ACFM) is an electromagnetic NDT technique capable of both detecting and sizing (length and depth) surface-breaking cracks in metals. The ACFM NDT technique alternates constant-current in a tangential solenoid, remote from the test surface, and induces electric currents in the sample surface, which are uni-directional and of uniform strength over a localised area under the solenoid. When no defects are present in this area, these electric currents will be undisturbed. If a crack is present, the uniform current is disturbed and the current flows around the ends and down the face of the crack. A standard PC is used to control the equipment and display results. ACFM is unique in the way data is displayed in this electromagnetic NDT process.