Overview
ISO 20339:2017 - Non-destructive testing - Equipment for eddy current examination - Array probe characteristics and verification - defines the functional and electrical characteristics of eddy current array probes and their interconnecting elements, and provides standardized methods for their measurement and verification. The standard enables well-defined descriptions, comparability and, where applicable, recommended acceptance criteria for array probe performance. It is intended to support consistent procurement, testing, calibration and verification of eddy current array equipment used in NDT (non-destructive testing).
Key topics and technical requirements
- Probe and interconnecting element definitions: terminology for elements, patterns, sequencing and thresholds to ensure consistent communication about array probes.
- Probe types and physical characteristics: description of surface and coaxial probe families, number/shape/spacing of elements, housing materials, facing thickness, mounting and position marks.
- Electrical characteristics: specified measurement of coil/element impedance, recommended excitation voltages and frequency ranges, and cable electrical properties (resistance, capacitive reactance per unit length).
- Functional characteristics: measurable properties for a defined system such as angular sensitivity, response to elementary discontinuities (holes, slots, deposits), coverage length/area per pattern, minimum detectable discontinuity size, penetration/penetration depth characteristics, lift-off effects and resolution.
- Verification and measurement methods: levels of verification, characteristics to be checked, measurement conditions and use of appropriate reference blocks for reproducible functional testing.
- Specific guidance for probe families: sections covering surface array probes (edge effects, slot/hole responses, lift-off, effective depth of detection, resolution) and coaxial array probes (axial response homogeneity, eccentricity and fill effects).
- Influence of interconnecting elements: assessment of multiplexers, amplifiers, cables, connectors, rotating heads and other active/passive components on probe performance.
- Safety and environmental conditions: temperature/humidity ranges, EMC tolerance and resistance to contaminants.
Practical applications and users
ISO 20339:2017 is essential for:
- NDT engineers and inspectors setting up eddy current array inspections.
- Manufacturers of eddy current probes and inspection systems for design verification and product specifications.
- Quality managers and procurement teams requiring objective acceptance criteria.
- Calibration and testing labs performing verification and routine checks.
- Industries using eddy current array testing: aerospace, automotive, power generation, oil & gas, rail and heavy industry where detection of surface/sub-surface defects is critical.
Practical benefits include improved comparability of probes, reproducible verification procedures, clearer acceptance criteria, and better interoperability between probes and instruments.
Related standards
Keywords: ISO 20339:2017, eddy current testing, eddy current array probes, array probe verification, non-destructive testing, NDT probe characteristics, reference blocks, probe measurement.