Which parameter is NOT typically measured in ET?

In the context of Eddy Current Testing (ET), the measurement of impedance, reactance, and resistance is central to determining the properties of the test material and detecting anomalies such as cracks or changes in conductivity. Impedance is the combined effect of resistance and reactance, and both reactance (the opposition to change in current flow due to inductance and capacitance) and resistance (the opposition to direct current) are crucial parameters that work together to characterize the electrical properties of the material under test.

Sound frequency, however, is not a parameter associated with Eddy Current Testing. Instead, it pertains more to methods like ultrasonic testing, where sound waves are utilized to detect flaws. ET relies on electromagnetic principles rather than acoustic waves, hence sound frequency does not play a role in the operation or interpretation of Eddy Current Testing results. This is why it is identified as the parameter that is not typically measured in ET.