Eddy current testing can be used for a wide range of applications. It is often applied for surface crack detection and material sorting. Material sorting is used to ensure that the proper materials are in use and to verify component materials or assembly features (such as the orientation or position of a subcomponent in an assembly). Flaw Detection It’s usually carried out with pencil probes or ‘pancake’ type probes on ferrous or non-ferrous metals. Frequencies from 100 kHz to a few MHz are commonly used. Depending on surface condition it is normally possible to find cracks 0.1 mm or less in depth. More complex are dual or multiple frequency inspections. These are commonly used for tubing inspection, in particular for suppression of unwanted responses due to tube support plates. Conductivity Measurement / Material Sorting For nonferrous materials such as aluminum and copper, eddy current electrical conductivity measurements are often used to verify material characteristics. For raw and processed materials conductivity measurement can determine the purity of the metal.