Eddy Current Testing

In this article, we will discuss Eddy Current Testing (Principle). So, let’s get started.

Eddy Current Testing

Eddy currents are defined as oscillating electrical currents
induced in a conductive material by an alternating magnetic field, due to electromagnetic induction.

ECT (Eddy Current Testing) is used for sorting materials, measurement and control of dimensions of tubes, sheets and rods and for pre-service and in-service examination of heat exchanger tubes.

Principle

• In ECT an AC ( 1 kHz – 2 MHz) is made to flow in a coil (probe) which in turn produces a magnetic field around it.
• This coil when brought close to the electrically conducting surface of a metallic material to be inspected, induces an eddy current flow due to
electromagnetic induction.
• The presence of any defect in the material disturbs the eddy current flow.
• This generates an alternating magnetic field ( in opposite direction) which may be detected as a voltage across a second coil or by the deviation of impedance of original coil.