It is required to perform a 3-point test with a sensitive voltage testing devices to verify a zero energy state. Examples of sensitive voltage testing devices include “proximity” testers, such as glow sticks (similar to light pens), tic-tracers (they make a sound), or direct-reading HV voltmeters.
A 3-point test consists of testing the voltage tester on a known energized source to verify it is working properly (Test No. 1).
Then, test the circuit on which work is to be performed (Test No. 2).
Finally, test the voltage tester on the same energized source as was used in Test No.1 to verify the tester is still working properly (Test No. 3).