Which of the following precautions should be taken when measuring in-circuit resistance with an ohmmeter?

• A. Ensure that the circuit is powered
• B. Remove all components from the circuit
• C. Short the capacitor before measuring
• D. Ensure that the circuit is not powered

Answer: (D)

When measuring in-circuit resistance with an ohmmeter, it is crucial to ensure that the circuit is not powered. This is because an energized circuit can produce false readings or damage the ohmmeter itself. An ohmmeter applies a small voltage to measure resistance, so if the circuit is powered, other voltages in the circuit can affect the measurement and potentially lead to incorrect results. Additionally, measuring resistance in a powered circuit can create safety hazards both for the technician using the meter and for the equipment being tested.

Taking this precaution helps ensure accurate readings and protects both the measurement device and the components being measured from unwanted current flow or damage.