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Inspection & TestingLesson Premium

Test instruments: safe isolation and trustworthy readings

Choose the instrument for the task, establish a safe test condition and recognise a suspect reading.

A meter displaying zero is not, by itself, proof that a circuit is safe to touch. Identify every supply, isolate and secure against reconnection, then prove dead using suitable equipment and the correct procedure. Check the voltage indicator on a proving unit or suitable known source before and after proving dead. A non-contact detector is not a substitute.

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