Probes Design
Surface
Surface probes are made with coils designed to be driven at relatively high frequencies (typically 50 kHz to 500 kHz). Using higher frequencies results in less penetration of the eddy current field into the test part, allowing the area directly below the surface of the part to be inspected. In addition, the higher frequencies provide a higher resolution for the detection of smaller defects.
Subsurface
The coils in subsurface probes are designed to be driven at relatively low frequencies (typically 1 kHz to 20 kHz). Using lower frequencies results in greater penetration of the eddy current field into the test part, allowing cracks or corrosion to be detected in thicker structures or in multilayer structures such as aircraft lap joints. Subsurface probes provide greater penetration; however, sensitivity to small defects decreases as the frequency and penetration are increased.
High Frequency, High Resolution
High-frequency, high-resolution probes provide both a high frequency and a high resolution in order to detectsurface-breaking defects on aluminum aircraft skins. These probes are made with 32 absolute coils positioned for the complete coverage of a 26 mm scan area. Although these probes are used for a specific application, they are very flexible and suitable for various high-frequency surface-breaking applications being developed.
