USCG Exam PracticeMaintenance, machine tools, drawings, and tables
A megohmmeter (megger) is used in engine room electrical maintenance. Which of the following correctly describes the proper procedure for its use?
- A. Connect in parallel across the circuit with the equipment energized to read insulation resistance
- B. Connect in series with the load while the circuit is energized to measure current leakage
- ✓ Apply to de-energized and discharged equipment; discharge again after the testCorrect
- D. Apply 120 VAC test voltage to the circuit and read resistance in ohms on the analog scale
Why C is correct
DOE-HDBK-1011 Vol.4 §14-1 states the megohmmeter applies a high DC test voltage (commonly 500–1000 V) to read insulation resistance in megohms, and that equipment must be de-energized and discharged before and after the test. Connecting it to an energized circuit or reading in ohms rather than megohms are incorrect procedures.