What type of reference standards are used for eddy current testing?

In eddy current testing, reference standards can vary significantly based on the specific requirements of the test system being used. The correct choice indicates that reference standards may contain either artificial or natural discontinuities, or they may be designed to be free of discontinuities altogether. This flexibility allows for a broader application of the test system.

Artificial discontinuities are often introduced in reference standards to calibrate or validate the testing equipment and to ensure that it can detect anomalies of known sizes and characteristics. These controlled conditions help in verifying the sensitivity and specificity of the eddy current test.

On the other hand, natural discontinuities represent real defects that may occur in materials, providing a realistic scenario for testing. In some cases, standards that are free of discontinuities are also relevant, especially when establishing a baseline for material properties without any influence from defects.

Thus, the comprehensive nature of this answer reflects the variability needed in reference standards based on the application of eddy current testing, ensuring that it remains applicable across diverse scenarios and specific testing requirements.