Two hand-held electrodes which are pressed against the surface of a part to make contact for passing magnetizing current through the metal. The current passing between the two contacts creates a field suitable for finding defects with magnetic particles.
If a part is too large to put onto a bench testing unit, then local magnetization can be done. One method of such local magnetization is by use of prods. These are usually copper posts on the ends of the conductors from the magnetic particle machine.
Discontinuities parallel to the line between the prods are made visible by the magnetic particles. This has long been a useful technique in MPI. It is readily portable and therefore convenient for field use. The sensitivity to subsurface defects is greater with this method than any other especially when using half wave rectified current.