How to use a multimeter to distinguish the live and neutral wires of AC power?
The simplest and most direct way to distinguish between the neutral wire and the live wire is to use a test pen to test. As the electrician's eyes, the electroscope pen is not only easy to operate, but also safe and reliable. In the absence of an electric test pen, we can also use a multimeter to distinguish the neutral line and the live line. The specific operation method is as follows:
Single meter pen test method
Set the dial of the pointer multimeter (digital meter) to the AC voltage of 500V. Hold the insulating end of the red test pen with your right hand and place the metal tip of the test pen against the wire being measured; pinch the metal tip of the black test pen with the fingers of your left hand. If the meter needle shows voltage (the voltage is related to the dryness of the skin, shoes, etc.), it means that the wire being measured is the live wire, otherwise it is the neutral wire.
Ground wire test method
Place the red test lead on the wire under test and the black test lead on the ground wire or a metal conductor that is in good contact with the earth. If the pointer indicates a voltage close to 220V or close to this value, it proves that the wire under test is a live wire. There is no voltage between the neutral wire and the ground, or there is only a few volts, but compared with the live wire, there is still a big difference.
Note: One test lead must be connected to the object being measured, and the other test lead must be connected to an object with good conductivity to the earth. If it is connected to a dry wall or the ground, the voltage may not be measured even if there is electricity.
Palm thread test method:
Wrap the black test lead several times around your left or right hand, and place the end of the red test lead on the wire being measured with the other hand. If the multimeter pointer deflects to the right and there is a certain voltage, it means the live wire; the wire with no response is the neutral wire. However, this method uses induced current to measure, which is easily affected by environmental magnetic fields or electric fields. The measurement results may not be accurate and are for reference only.
Summarize
Although the above methods can all determine whether the neutral wire, live wire and objects are charged, they all have certain shortcomings.
For example, in the first method, if the skin is very dry and the shoes have good insulation, the voltage displayed by the multimeter may be very low, which will affect the judgment of the result.
For example, in the second case, if the ground wire is disconnected or another conductor connected to another test lead is not in good contact with the earth, it may also cause misjudgment.
For example, in the third type, if there is a strong magnetic field or electric field around, the measurement results will be completely inaccurate.
