Factors Affecting Spatial Resolution in Pulsed Eddy Current Inspection of Pipe

Pulsed eddy current is an emerging technique for measuring wall thinning of steel under insulation. Ideally, it would be desirable to obtain the most localised information of pipe condition possible. The localization of information is constrained by the flow of eddy currents in the pipe. This in turn is heavily influenced by the orientation of the probe. This paper examines three different probe orientations, representative of all probe types for their influence on eddy current flow. All three orientations will have difficulty accurately measuring highly localized thinning, because the eddy currents that give rise to their signal spread out rapidly way from the thin region in the long time signal decay. Of the three orientations, the longitudinal one does the best job of localizing the eddy currents directly under the probe.