What action should be taken first during live-dead-live testing?

The first action during live-dead-live testing is verifying the operation of the test instrument on a known voltage source. This step is crucial because it ensures that the testing device is functioning properly before any testing is performed on the live circuit. If the instrument is not calibrated or is malfunctioning, it can lead to unreliable measurements or even hazardous situations. By confirming the accuracy and reliability of the test instrument against a known voltage source, you ensure that when you perform the live-dead-live test, the results will be valid and safe.

Taking this preliminary step helps to protect the technician from potential electrical hazards and ensures the integrity of the testing process. Once the instrument's operation is verified, subsequent steps, such as testing the conductor for an unknown voltage, can be executed with greater confidence in the results. Properly performing this sequence is fundamental in establishing safety and reliability in electrical measurement practices.