Current Flow (CF)

Current flow techniques produce a circular magnetic field by passing a current through the test piece, i.e. concentric rings of magnetic lines of force radiate at 90° (perpendicular) to the current flow.

The current flow is normally obtained from a transformer supplying A.C. or a transformer rectifier for D.C.

The output voltage of current flow equipment is so low that there is no risk of electrical shock to the operator from the equipment’s specimen contact points or test specimen.

The choice of power supply depends on the test requirements, i.e. using A.C. will reveal discontinuities up to approximately 1 mm below the surface, using D.C. will reveal discontinuities typically up to 2 mm to 3 mm below the surface.

An ammeter is usually incorporated in the equipment to indicate the amount of current flowing through the workpiece.

In fixed installations, i.e. bench equipment, the component is firmly clamped between contact heads. With portable equipment, electrical contact is made using prods and/or clamps.