What is the role of the test coil in ET?

The test coil in electromagnetic testing (ET) serves a critical function by generating the electromagnetic field that induces eddy currents in the conductive materials being tested. When alternating current flows through the test coil, it creates a varying magnetic field around it. This magnetic field penetrates the conductive material, inducing eddy currents within the material itself. The presence and behavior of these eddy currents provide valuable information about the material's properties, including its conductivity and the presence of any flaws or discontinuities. Thus, the test coil is essential for establishing the conditions necessary for measuring the responses of the induced eddy currents, which are then analyzed to assess the integrity of the material under inspection.