AC Voltage tester pen to measure in-phase or out-of-phase of phase lines
Circuits that do not distinguish between wire colors are definitely a headache when repairing. Single-phase circuits are okay, but if you encounter three-phase circuits, it's really a big head! However, the electric pen has a magical function that can easily help you to measure the in-phase or out-of-phase of phase lines.
When measuring, hold an electric pen in each hand and stand on an insulating object. Touch the two electric pens to the two wires at the same time. If the brightness of the two electric pens is low, it means that the two wires measured at this time are in phase (both phase wires). If the brightness of the two pens is high, it means that the two lines measured at this time are out of phase (one phase line and one neutral line). In this way, three phase wires and one neutral wire in a three-phase circuit can be quickly screened out.
