Phase angle shift
The phase angle shift is the temporal shift between excitation signal and sensor signal in eddy current testing. It helps separate different influence variables such as crack size and lift-off.
Physical-Chemical Mechanism of Action
Phase angle shift occurs due to the different response speed of the material to the eddy current field. The excitation signal (e.g., an electric field) and the sensor signal (the material's response) are shifted in time, resulting in a phase difference.
Metallurgical Relevance & Risks in Welding
The phase angle shift is important for accurate detection of cracks and material defects. An inaccurate shift can lead to errors in crack detection, which affects confidence in the inspection. There is also a risk that smaller or deeper cracks may not be detected.
Workshop Practice & Action Instructions
To ensure accurate phase angle shift, the equipment must be properly calibrated and set up. The excitation signal frequency should typically be between 10 kHz and 20 kHz. It is important that the sensor signal is correctly aligned in time with the excitation signal to ensure precise measurement.