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Material of an eddy current reference standard

Aviation Mechanic General (AMG) practice question 17 of 21 on Inspection Concepts and Techniques. ACS element AM.I.K.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA reference standard used to calibrate eddy current test equipment must be made from what material?

  1. AThe same material as the item to be tested
  2. BA nonconductive material such as plastic
  3. CAny ferromagnetic material, regardless of the item's alloy
Show the answer and explanation

Correct answer: A. The same material as the item to be tested

  • A — correct The handbook states that a reference standard for eddy current calibration is made from the same material as the item to be tested and contains known flaws or cracks.
  • B — incorrect Eddy currents can be induced only in electrically conductive material, so a nonconductive standard could not produce a calibration response.
  • C — incorrect The standard must match the material of the item under test; ferromagnetism is a requirement of magnetic particle inspection, not of eddy current calibration.

BACKGROUND

An eddy current test instrument performs three basic functions: generating, receiving and displaying. Because flaws or thickness changes alter the impedance of the test coil, the instrument must be calibrated against a known reference. A reference standard is required for this calibration and is made from the same material as the item to be tested. It contains known flaws or cracks and may include features such as a flat surface notch, a fastener head, a fastener hole or a countersink hole so that the instrument's response can be related to the actual part.

STUDY TIP

For any NDI calibration question, the reference standard mirrors the part: same material, and for ultrasonics the same configuration.

KEY POINTS

  • Eddy current equipment must be calibrated with a reference standard.
  • The standard is made from the same material as the item being tested.
  • It contains known flaws such as notches, fastener holes or countersinks.

SOURCES

  • FAA-H-8083-30B ch10 "Eddy Current Instruments"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.