Pulsed Eddy Current 

PECPulsed Eddy Current is an electromagnetic inspection technique which allows the measurement of wall thickness in low alloy steels without the need to remove insulation or to prepare rough and dirty surfaces.

A transmitter coil produces a magnetic pulse which induces eddy currents within the component wall. The eddy currents in turn produce a second magnetic pulse which is detected by the receiving coil. The eddy current density decays as they progress deeper into the component wall but the speed of decay is increased when they reach the far surface. The system monitors the rate of decay of the eddy current pulse within the steel wall. The average wall thickness over the area of measurement is derived from the comparison of the transient time of certain signal features with signals from known calibration pieces.

The larger the stand-off of the coil from the component ie the thicker the insulation, the larger the footprint of the measurement and the larger the area of corrosion needs to be before detection is achieved.

For more information on PEC see:
'MFL and PEC tools for plant inspection',
J H J Stalenhoef and J A De Raad, Insight Vol 42 No 2, 2000, pp 74-77
'Pulsed Eddy Current in Corrosion Detection',
M A Robers and R Scottini, 8th ECNDT, Barcelona, June 2002, available at

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