Frequency Response
Frequency response describes how an eddy current signal varies with the test frequency, governed by the standard depth of penetration (skin effect) and used to select frequencies that optimize defect detection at the target depth.
Definition
Higher frequency confines eddy currents near the surface (high sensitivity, low penetration); lower frequency penetrates deeper at the cost of sensitivity. Standard depth of penetration δ = √(ρ/(π·f·μ)).
Related terms
- Multi-Frequency Eddy Current — Multi-frequency eddy current testing uses two or more simultaneous frequencies whose responses are mixed in software to suppress unwanted variables (support-plate signals, tube-end effects) and isolate the defect signal of interest.
- Impedance Plane — The impedance plane is a 2D display in eddy current testing showing the probe coil's resistive (X-axis) and inductive reactive (Y-axis) components, on which signals from lift-off, defects, and conductivity changes trace characteristic vectors.
More physics terms
Back-Wall Echo · Beam Spread · Near-Field · Far-Field · Dead Zone · Shear Wave · Longitudinal Wave · Surface Wave · Lamb Wave · Mode Conversion
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.