Simultaneous Measurement of Material Properties and Thickness of Carbon Steel Plates Using Pulsed Eddy Currents

OF CARBON STEEL PLATES USING PULSED EDDY CURRENTS V.O. de Haan and P. de Jong 1 BonPhysics Research and Investigations BV, Putterhoek, The Netherlands; 2 Röntgen Technische Dienst bv, Rotterdam, The Netherlands Abstract: It is well know from literature that Pulsed Eddy Currents generated by switching off a stationary current through a coil above a carbon steel plate can be used to measure the thickness of this plate. The procedure is to measure the induction voltage signal of a receiving coil for a known reference thickness and compare this to the signal from an unknown thickness. The disadvantage of this method is that a reference measurement is needed and the result is influenced by a change in material properties. The authors present a method using the same technique but a different signal interpretation method, enabling the simultaneous determination of material properties and thickness. A description of the signal interpretation method is given. It is shown that for several types of carbon steel an accuracy of 10% can be achieved. Introduction: The pulsed eddy current method RTD-INCOTEST is based on measurement of an induction voltage, U(t) in a receiving coil as function of time, t . This voltage is created by the slowing down of the eddy currents generated in the object by means of a suddenly switched off current, I through a transmitting coil (see figure 1).