What distinguishes absolute from differential Eddy Current Testing?

The distinction between absolute and differential Eddy Current Testing lies in the way the signals are measured and utilized. In absolute testing, the probe measures the total impedance or signal from the component being tested, giving a direct indication of the material characteristics and potential defects based solely on that single measurement. This method provides crucial information about the overall condition of the material.

On the other hand, differential testing involves two probes. It measures the signal from the test material using one probe while using the second probe to evaluate a reference signal, often from an adjacent area or a standard material. The comparison of these two signals allows for the detection of variations that indicate imperfections or changes in material properties. This approach is particularly adept at identifying subtle differences that might be masked in absolute testing, which relies on baseline characteristics rather than comparative analysis.

The correct answer reflects the fundamental difference in methodology: absolute testing relates to measuring overall signals while differential testing focuses on comparing those signals.