Surface Coil
A surface coil is a small handheld eddy current probe used to scan accessible surfaces of components — typically a pencil-style absolute or reflection probe — for surface-breaking crack detection.
Definition
Surface coils are the workhorse of weld and fastener inspection in aerospace and structural NDT. Pencil probes for tight access, sliding probes for weld toe scanning, and shielded probes for sensitivity-critical work are all variants.
Related terms
- Encircling Coil — An encircling coil is an eddy current probe configuration in which a circular coil surrounds the outside of a tubular or wire product, inspecting the full circumference simultaneously as the product passes through.
- Bobbin Coil — A bobbin coil is a differential or absolute eddy current probe that travels axially inside a tube, inspecting the entire tube circumference simultaneously for wall loss, pitting, and through-wall defects.
- Eddy Current Testing (ET) — Eddy Current Testing (ET) is an electromagnetic NDT method that induces circulating currents in conductive materials using an AC coil; changes in coil impedance reveal surface and near-surface defects, conductivity variations, and coating thickness.
Further reading
eddy current testing complete beginner guide
More equipment terms
Calibration Block · Transducer · Dual-Element Probe · Angle-Beam Probe · Normal-Beam Probe · Couplant · Reference Reflector · Side-Drilled Hole · Flat-Bottom Hole · Notch Reference
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.