USCG Exam PracticeHand/power tools, measuring instruments, and maintenance
A series ohmmeter's scale reads zero ohms at full-scale deflection and infinity at no deflection. Before use, the technician shorts the leads and adjusts the meter to read zero. What is the purpose of this zero-adjustment procedure?
- A. To calibrate the meter's voltage coil against the current coil
- ✓ To compensate for aging of the meter's internal battery, which reduces available currentCorrect
- C. To set the meter's range switch to the correct resistance band
- D. To discharge any residual capacitance in the circuit under test
Why B is correct
In a series ohmmeter, zero ohms gives full-scale deflection. The leads are shorted and the meter is zero-adjusted before use to compensate for battery aging, which reduces the internal source current and would otherwise cause an erroneously high resistance reading.
Cited:NEETS Mod. 3 §1-3