What are the two main types of Eddy current tests?

The two main types of Eddy current tests are absolute measurements and differential measurements. In absolute measurements, the eddy current instrument measures the absolute value of the impedance change in the test conductors, which helps in determining the condition of the material under inspection. This method provides a direct reading of the conductive material’s properties, such as thickness and conductivity.

On the other hand, differential measurements involve using two probes or coils. This approach measures the difference in impedance between two points, allowing for better discrimination of cracks or defects by canceling out variations in the material that are not related to the flaws. This is particularly useful in identifying small defects or those in thin materials, as it enhances sensitivity to localized changes in the eddy current field.

Understanding these two main types allows practitioners to choose the appropriate technique based on the material and the specific inspection requirements.