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Megger for insulation resistance

Aviation Mechanic General (AMG) practice question 7 of 41 on Fundamentals of Electricity and Electronics. ACS element AM.I.A.K9 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhich instrument is a high-range ohmmeter containing a hand-operated generator and is used to measure insulation resistance?

  1. AAn electrodynamometer wattmeter
  2. BA D'Arsonval ammeter with a shunt
  3. CA megger (megohmmeter)
Show the answer and explanation

Correct answer: C. A megger (megohmmeter)

  • A — incorrect The electrodynamometer movement is used for AC measurement and in wattmeters; it does not contain a hand-driven generator for high-resistance testing.
  • B — incorrect A D'Arsonval ammeter measures current and uses a shunt to extend its range; it is not designed to measure insulation resistance.
  • C — correct The megger is described as a high-range ohmmeter with a hand-operated generator, used to measure insulation resistance and other high-resistance values.

BACKGROUND

The megger, or megohmmeter, is a high-range ohmmeter containing a hand-operated direct-current generator. It is used to measure insulation resistance and other high-resistance values, and also for ground, continuity, and short-circuit testing of electrical power systems. Its chief advantage over an ordinary ohmmeter is its ability to measure resistance with a high potential, or breakdown voltage, which verifies that insulation or a dielectric will not short or leak under electrical stress. The instrument portion uses two opposed coils, so its indication is independent of the generator voltage.

STUDY TIP

Associate the megger with insulation testing under high voltage; an ordinary ohmmeter cannot reveal insulation that leaks only under potential.

KEY POINTS

  • A megger is a high-range ohmmeter with a hand-driven generator.
  • It measures insulation resistance and other high-resistance values.
  • Its advantage is testing at a high breakdown voltage.

SOURCES

  • FAA-H-8083-30B ch12 "Megger (Megohmmeter)"
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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.