Check whether the electrical appliance is connected to the protective grounding wire. For electrical appliances with good insulation performance between the metal casing and the power supply circuit, the metal casing should be measured when the 220V AC power is connected to work normally. If the light-emitting diode inside the test pen does not emit light, it means that the housing of the electrical appliance is connected with a good protective grounding wire (or connected to the neutral wire); if the light-emitting diode inside the electrical measuring pen glows, it means that the protective grounding wire is not connected to the housing of the electrical appliance, or the wiring already opened. In order to ensure personal safety, a good protective grounding wire should be connected to the housing of the electrical appliance as required. It should be pointed out here that when the metal shell of the electrical appliance is detected, the light-emitting diode inside the test pen emits light. It is not that the electrical appliance's casing has been leaked with 220V alternating current, but because the electrical appliance's casing is not connected to the ground wire, so The generated very weak induced voltage makes the light-emitting diode inside the pen glow brightly. In the same way, insert the probe of the test pen into the protective grounding wire (or the protective neutral wire) jack of the 220V three-hole power socket. If the LED inside the test pen does not light up, it means that the protective grounding wire (or the neutral wire) is in good condition. ; If the light-emitting diode glows, it means that the protective grounding wire jack of the socket is ineffective, it may be that the protective grounding wire has been opened, or the protective grounding wire may not be connected.
