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

When measuring in-circuit resistance with an ohmmeter, it is essential to ensure that the circuit is not powered. This precaution is crucial because if the circuit is powered, the presence of voltage can affect the readings of the ohmmeter and potentially damage the meter itself. An active circuit can introduce unexpected behaviors, such as backfeeding voltage, which can lead to inaccurate resistance measurements or even create unsafe conditions for both the equipment and the user.

By ensuring the circuit is powered down, you can obtain an accurate measurement of resistance without interference from voltage or current. This safety measure helps in obtaining reliable data and prevents any electrical hazards that might result from inadvertently measuring resistance in a live circuit.