Tick tracer. Glow meter. Sniffer. They go by many names, but capacitive voltage sensors are all designed to do one thing: detect the presence of voltage in a wire or piece of equipment without actually making direct contact with the conductor or energized part. These test tools are popular because they're inexpensive, easy to use, and small enough to fit in a shirt pocket.

As a result, the sensing circuit in the tester detects voltage and signals to you via a lamp, *tone, ticking noise, or buzzer* that voltage is present.

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