What is essential for limit frequency equations to be useful?

Limit frequency equations are crucial for understanding how the frequency of an Eddy current affects the testing results. To get accurate and meaningful data from these equations, it is essential to use them in conjunction with their impedance diagrams. The impedance diagrams visually represent the variations in impedance as frequency changes, providing insights into how the material's properties are influenced by Eddy currents.

When analyzing data, these diagrams help engineers understand the responses of different materials at various frequencies, including how defects or changes in the material affect the impedance. Simply using the limit frequency equations without understanding the associated impedance diagrams would not yield a complete picture of what the Eddy current testing results imply. Thus, the correct answer focuses on the necessity of integrating limit frequency equations with impedance diagrams to provide a comprehensive analysis in Eddy Current Testing.