What does the term "crossover" indicate in Eddy current testing?

In Eddy current testing, the term "crossover" specifically refers to the point where the measurement signal crosses zero. This is significant because it indicates a change in the condition of the material being tested. When the signal crosses zero, it often suggests a transition in the electrical properties of the material, which may be an indication of defects, changes in thickness, or variations in conductivity caused by flaws such as cracks or corrosion. Understanding this signal is critical for interpreting the results of the eddy current tests and making informed evaluations regarding the integrity of the tested materials.