Amprobe ST-102B GFCI Outlet Tester - Electrical Socket Tester for Home & Commercial Use - Safety Test for 120V AC Receptacles - Perfect for Electricians, DIY & Home Maintenance

This circuit breaker tracer works perfectly but you MUST follow the instructions. The unique auto-calibration system ensures that the correct breaker is identified every time without any false indications.Most devices like this suffer from problems with "false positives", meaning they beep at more than one circuit breaker and it's difficult to tell which one is actually powering the circuit you are working on. These false positives occur because the transmitter signal can be induced into other wires if they run parallel to the circuit under test. This occurs frequently in homes and businesses because all the wires must eventually go back to the breaker panel and many follow the same path to get there.This device uses a 2-step identification process to eliminate those false positives. When powered up, the device starts out at a high sensitivity level, meaning it will detect the transmitter signal even if it's weak from a far-away transmitter or caused by an "induced" signal. After the transmitter is plugged into the powered outlet, you slowly scan ALL the circuit breakers with the device to set the calibration level, disregarding any beeps. Each time the device detects a signal and beeps, it resets it's sensitivity threshold to match that signal. If it encounters another higher level signal it resets to that higher signal. In this way, by the time you are done scanning all the breakers the tester has set itself so that only the very highest signal in the circuit breaker box will activate it. This is what guarantees that when you make the second pass, only one circuit breaker, the one with the transmitter plugged in, is identified.I tested this in a breaker box where all the circuits were already identified. In every case the first pass through the box yielded several beeps, as circuits with induced signals were detected. But also in every case, the second pass through the box correctly identified the circuit under test, with no false positives.There is one drawback to this particular tester - the power switch is too sensitive and it takes a very light touch to turn it on. Just holding the device it's possible to turn it on accidentally and if it's left in a portable tool box it's likely to be turned on by jostling around. It will turn itself off after a delay, but it would be better if the on/off switch was not so sensitive.