A review of the alternating current field measurement inspection technique

Abstract

This paper describes the principles of the a.c. field measurement technique, a non‐contacting electromagnetic method of crack detection and sizing in metals. The development of the technique is covered, followed by examples of some of the many different applications the technique has been used for, including multi‐sensor arrays for rapid manual inspection or for deployment by robotic manipulator in hazardous environments. Finally, recent work on replacing the normal multi‐turn coil magnetic field sensors with newly available GMR sensors is discussed.