AiVibeQuality, Reliability & Maintenance
Eddy Current Testing (ET)
Eddy current testing is an electromagnetic non-destructive testing method that induces circulating currents in conductive materials with an alternating magnetic field and detects changes in those currents caused by cracks, corrosion, material variations or coating thickness.
A probe coil carrying alternating current creates a changing magnetic field that induces eddy currents in a nearby conductive part. Defects, changes in conductivity or permeability, and variations in the distance between probe and surface alter the eddy current flow, which changes the coil's impedance. Instruments display these changes, often on an impedance plane, allowing trained inspectors to distinguish defect signals from other effects. Eddy currents concentrate near the surface, and their depth of penetration decreases as test frequency, conductivity and permeability increase.
ET is widely used in aerospace to detect fatigue cracks around fastener holes and in wheels, in power and process plants to inspect heat exchanger and condenser tubes, and in manufacturing to sort materials, check heat treatment and measure the thickness of non-conductive coatings. Array probes cover larger areas quickly, and the method needs no couplant and little surface preparation, making it suitable for automated inline testing of tubes, bars and wire.
ET works only on electrically conductive materials and is mainly sensitive to surface and near-surface defects. Ferromagnetic materials are more difficult to inspect because of permeability variations. Reliable results need reference standards with known artificial defects, careful probe selection and qualified operators. ISO 15549 gives general principles for eddy current testing.
Key points
- Induces eddy currents and detects changes caused by flaws or material variations.
- Most sensitive to surface and near-surface defects in conductive materials.
- Used for aerospace cracks, heat exchanger tubes and coating thickness.
- Needs reference standards with known artificial defects.
Where AiVibe comes in
AiAmbA AI Factory use cases include predictive maintenance and visual inspection on textile, automotive and electronics lines. AiAmbA IoT normalises industrial signals from protocols such as OPC UA and MQTT, with driver availability confirmed per installation.
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