Nondestructive testing Eddy current device with Lissajous display

摘要

Eddy current device comprises an injector (22) for generation of an excitation current, which is fed to a sensor coil (20). The coil output (21) is connected to a delay device (23), which is controlled by a delay controller (25). The delay output is fed to an inverter (24) and summing circuit (26). The resulting differential signal is visualized as a Lissajous (29) figure. An alternative to an analogue inverting and summation circuit is using a digital sampling circuit. Use of the controlling circuitry permits the use of a single coil in a differential manner.