Before using a megohmmeter to check a cable, what must the electrician ensure?

When preparing to use a megohmmeter for checking a cable, it is critical for the electrician to ensure that the circuit is de-energized and has been properly locked and tagged out, as well as tested. This process is crucial for safety and accuracy.

Megohmmeters apply a high voltage to the insulation of the cable being tested, and if the circuit is still energized, it poses a serious safety hazard to the technician. They risk electrical shock or injury due to live voltage. Locking and tagging out the circuit ensures that no one can accidentally energize it while the test is being performed. Additionally, testing the circuit for voltage before making these checks confirms that it is indeed de-energized.

Performing this preliminary safety step allows for a more accurate test of the insulation quality of the cable without the interference of live electrical energy.