New methods of signal excitation and processing in magneto-inductive testing of structures and alloys

This paper describes some results of applying noise excitation to eddy current testing. Pseudo random binary sequences (PRBS) were used as a noise equivalent. The advantage of this technique compared with conventional methods is mainly the simplicity of the equipment used. It is possible to produce a device using noise excitation on the basis of a microcalculator. Also, this technique gives a direct comparison between the reference object and the object under test as in the well known CS (controlled signals) method. The performance of the PRBS method is compared with a multifrequency eddy current method by solving the problem of separating various grades of steel. Both methods show nearly the same results.