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

When measuring circuit resistance with an ohmmeter, it is essential to ensure that the circuit is not powered because an active circuit can produce unpredictable readings and potentially damage the ohmmeter. Ohmmeters work by applying a small voltage to the circuit and measuring the resulting current to calculate resistance, so powered components can interfere with this measurement, leading to inaccurate results or even harming the measuring device.

In contrast to ensuring that the circuit is not powered, concerns such as verifying applied voltages, grounding, or frequency operation are not relevant in this context for resistance measurement. Resistance measurements are taken within an isolated circuit free from any power to provide accurate readings without risk of injury or equipment damage.