Eddy Current Testing and Their Value in Other Testing Methods

The underlying principle in most generators and electric motors would be magnetism. This is the force that is responsible for managing a wide range of eddy current instruments too. Eddy current is useful because it can cover large surface areas within a short time. It is identified as one of the quickest ways of measuring thicknesses, and even the impact heat has on various equipment. Also, eddy current testing doesn’t need any coupling liquids. This makes it easy to use eddy current for checking conductivity and hardness in metals. However, it is important to note that the use of eddy current testing is limited to materials that can conduct electric energy. Thus, this form of testing cannot be used on liquids. 

In some interesting situations, ultrasonic testing is executed with the help of an eddy current. Both of these methods complement one another. The ability of ultrasonic waves to penetrate deep surfaces, and the quick surface testing property of eddy currents - makes it easy to test certain applications. 

How does Eddy current testing work?

Eddy Current testing strongly depends on a phenomenon known as electromagnetic induction. 

  1. An alternating current is made to flow through a wire coil. 
  2. The coil generates an oscillating magnetic field. 
  3. If the magnetic field and the probe are moved near a conductive material, a flow of electrons will be seen. The flow of electrons will be circular. This is also known as eddy current. 
  4. When the eddy current flows into the conductive material, it creates a separate magnetic field. This will start to interact with the coil. 
  5. If the metal surface has changed in thickness or any issues on the surface (including cracks), they will alter the pattern and amplitude of the eddy current. Likewise, the magnetic field created will also be affected during the process. This is how eddy current is used to determine the thickness of various materials. 
Many factors can affect the overall results of eddy current inspections. For example, the current flows at a different rate along the surface of the material. And, if the surface has defects, the conductivity will increase. Before using eddy current for testing materials, any factor that can deviate results needs to be identified. 

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