CSLB C-10 Electrical ContractorSafety and TestingEasy
Which type of meter is essential for testing the integrity of insulation on high-voltage cables or motor windings?
- AClamp-on Ammeter
- BMegohmmeter (Megger)
- CContinuity Tester
- DPhase Rotation Meter
Show answer & explanationAnswer & explanation
Correct answer: B. Megohmmeter (Megger)
A megohmmeter, often called a 'Megger,' is specifically designed to measure very high resistances (in megohms) by applying a high DC voltage. This makes it ideal for testing the integrity of insulation in cables, transformers, and motor windings, identifying potential breakdowns or degradation.
Why the other options are wrong
- A. A clamp-on ammeter measures current, not insulation resistance.
- C. A continuity tester checks for a complete circuit (low resistance), not insulation integrity.
- D. A phase rotation meter determines the phase sequence of a three-phase system, not insulation integrity.
Megohmmeter (Megger)
An electrical test instrument used to measure very high electrical resistances, typically in megohms, by applying a high DC voltage. It is primarily used to test the integrity of insulation in electrical systems.
- Applies high DC voltage (e.g., 500V, 1000V).
- Measures insulation resistance to detect faults.
- Essential for preventative maintenance and troubleshooting of high-voltage equipment.
Memory trick: Insulation needs Megger, Continuity needs Buzzer, Phases need a Spinner.