When measuring resistance with a multimeter, what must be true about the circuit?

When measuring resistance with a multimeter, what must be true about the circuit?

• A. The circuit must be de-energized
• B. The circuit must be powered
• C. The circuit must be at operating temperature
• D. The circuit must be connected to a battery

Answer: (A)

When you measure resistance with a multimeter, the circuit must be de-energized. The meter in resistance mode sends a small test current through the path and measures the resulting voltage to determine resistance. If the circuit is powered, that external voltage can interfere with the meter’s test current, giving an inaccurate reading or even risking damage to the meter or its fuse. Any stored energy, like in capacitors, should also be discharged to avoid hazards and inaccurate results. The other scenarios—being powered, operating at a specific temperature, or having a battery connected—aren’t required and can skew the measurement.

When you measure resistance with a multimeter, the circuit must be de-energized. The meter in resistance mode sends a small test current through the path and measures the resulting voltage to determine resistance. If the circuit is powered, that external voltage can interfere with the meter’s test current, giving an inaccurate reading or even risking damage to the meter or its fuse. Any stored energy, like in capacitors, should also be discharged to avoid hazards and inaccurate results. The other scenarios—being powered, operating at a specific temperature, or having a battery connected—aren’t required and can skew the measurement.