Eddy current probes induce detectable eddy currents in ferrous and nonferrous material for flaw detection, weld inspection, and other nondestructive test applications. Two different detection formats are available: absolute and differential. Absolute detection uses a single pickup coil for flaw and crack detection and can detect both gradual and sharp changes. With differential detection, the detection of two pickup coils is compared for a greater resolution of sharp discontinuities or flaws.  The differential nature makes this type of probe less suitable for detection of gradual changes in material.