USCG Exam PracticeHand/power tools, measuring instruments, and maintenance
A series ohmmeter is zeroed by shorting the leads before use. This zero-adjustment procedure compensates for which specific condition, and what does full-scale deflection on a series ohmmeter indicate?
- A. It compensates for external circuit voltage; full-scale deflection indicates infinite resistance
- ✓ It compensates for battery aging; full-scale deflection indicates zero ohmsCorrect
- C. It compensates for temperature variation in the component under test; full-scale deflection indicates the rated resistance
- D. It compensates for lead resistance only; full-scale deflection indicates the resistance of the shorted leads
Why B is correct
NEETS Mod. 3 §1-3 states that in a series ohmmeter, zero ohms gives full-scale deflection so the scale reads backwards and is non-linear, and the leads are shorted and zero-adjusted before use to compensate for battery aging. Battery aging changes the internal EMF, which would otherwise shift the zero point.
Cited:NEETS Mod. 3 §1-3