Velocity induced eddy current inspection is a technique to inspect conductive materials. It has a good detection performance and is particularly well suited to situations where the speed is a factor to be considered because its sensibility increases with the moving speed1,2. The basic physical phenomena of this method, is based on the interaction of a stationary magnetic field and a specimen which moves with a constant speed in relation to that field. In the work presented in this paper the probe consists of a permanent magnet that induces eddy currents inside the specimen due to the motion and a Hall sensor to measure the resultant magnetic field in the vicinity.
The literature 3-5 mentions that the performance of the method depends greatly on the configuration of the magnets included in the probe and also in the assessment of the magnetic field. Enhancements can be achieved not only by increasing the magnetic flux density in the material to be inspected, but also, by choosing the best position for the magnetic sensors. This paper reports results obtained with an array of cubic magnets that have alternating vertical magnetization.