What type of eddy current probe operates without direct contact with the test surface?

An air-coupled probe operates without direct contact with the test surface by utilizing the principles of eddy current testing in conjunction with air as a coupling medium. This type of probe creates an electromagnetic field that induces currents in conductive materials without needing to physically touch them. This allows for the inspection of delicate or easily damaged materials where contact might cause harm or affect the test results.

The ability to operate without contact is particularly beneficial in applications where maintaining the integrity of the surface is critical, or where the surface conditions may not be ideal for contact probes. In contrast, contact probes, plug-in probes, and surface probes are designed to work while being physically in contact with the test piece, which limits their use in certain scenarios.