What is the function of the test coil in Eddy Current Testing?

In Eddy Current Testing, the test coil serves a critical function by inducing eddy currents in the test material. When an alternating current flows through the coil, it creates a changing magnetic field. This varying magnetic field penetrates the test material, which causes the electrons within the material to circulate, producing secondary currents known as eddy currents. These eddy currents can provide information about the conductivity and structural integrity of the material being tested.

Understanding the induction of these currents is essential because fluctuations in their magnitude and phase can indicate the presence of flaws or discontinuities within the material. Consequently, the health of the material can be assessed, allowing for preventive measures to be taken if necessary. This induction process is key to effectively utilizing Eddy Current Testing in various applications, including detecting cracks, measuring coating thickness, and assessing material properties.