USCG Exam PracticeHand/power tools, measuring instruments, and maintenance
When using a multimeter to measure resistance in a shipboard circuit, the technician must first ensure the circuit is:
- A. Energized and under normal operating load
- ✓ De-energized and isolated from all power sourcesCorrect
- C. Connected to a known reference voltage
- D. Set to the highest range before connecting leads
Why B is correct
An ohmmeter uses its own internal battery as a current source; external voltage on the circuit will produce false readings or damage the meter. The circuit must be de-energized and isolated before resistance measurement. (NEETS Mod. 3 §1-3)
Cited:NEETS Mod. 3 §1-3