What procedure should be followed when testing a circuit with an ohmmeter?

When testing a circuit with an ohmmeter, it is essential to remove all power from the circuit before performing any measurements. This is because an ohmmeter works by supplying a small voltage to the circuit to measure resistance, and if the circuit is powered, it can lead to inaccurate readings. Additionally, testing with power on can result in damage to the ohmmeter or create safety hazards, including electric shock.

By ensuring that the circuit is de-energized, you can safely and accurately measure the resistance across components. This procedure is a fundamental practice in both electrical troubleshooting and repair, ensuring that the technician is working in a safe environment and that the readings obtained are reliable.