Non-Destructive Testing (NDT) Practice Test

What constitutes the second circuit in the eddy current inspection setup?

1. A different probe connected to the same instrument

2. An isolated power source

3. Any conductive material in contact with the eddy current probe

4. A separate detection device

The correct answer is: Any conductive material in contact with the eddy current probe

In eddy current inspection, the second circuit is formed by the conductive material that interacts with the eddy currents generated by the probe. When the probe is placed near a conductive surface, the alternating magnetic field from the eddy currents induces additional currents in that material. These induced currents create their own magnetic field, which alters the original eddy currents. This interaction is crucial for the inspection process because the changes in the current flow and magnetic field can be analyzed to detect defects or variations in material properties. This makes the conductive material in contact with the eddy current probe an integral part of the inspection setup, as it completes the circuit that allows for effective inspection and analysis. The other options do not accurately represent what constitutes the second circuit in eddy current inspection. A different probe connected to the same instrument refers to a change in probes rather than circuit configuration, an isolated power source does not create a circuit necessary for data capture, and a separate detection device operates independently from the primary eddy current setup, rather than being part of the second circuit involved in the inspection process.