How to identify the neutral wire and live wire when you forget to bring a test pen and only have a multimeter
The limitations of electric pens are very obvious, especially those with digital displays, which sometimes make us misjudge. The light is too strong, and due to reflection, it is difficult to see clearly. The light is too dim, and the numbers are too small to see clearly. There are too many displayed numbers, flickering, fluctuating, making it difficult for you to accurately determine the voltage level. The sound and light induction pen only knows if there is electricity, but cannot know what the voltage is. The neon bulb electric pen can only be tested outdoors at noon, and there will be accidents sooner or later.
As an electrician, you may not have a pen, but you cannot do without a multimeter. The reason why a multimeter is called a multimeter is because of its powerful functionality. A good multimeter can help us achieve twice the result with half the effort during maintenance and repair.
A friend asked, without an electric pen, how can I use a multimeter to distinguish between neutral and live wires? For electricians, this is a kindergarten issue. Below is my sharing.
Firstly, determine if your work environment has a grounding wire. If there is a grounding wire, the operation will be very simple.
When the power supply is three-phase five wire, we set the multimeter to the highest AC voltage level and test the voltage between the five wires separately. The two wires with a voltage of 380 are both live wires, while the one with a voltage of 220 is a live wire and the other is a neutral wire. When the voltage is zero or very low, one is a neutral wire and the other is a ground wire.
When the power supply is single-phase three wire, set the multimeter to AC mode 220V and test the voltage between each two wires separately. The two wires with voltage or very low voltage are the neutral wire and the ground wire, and the remaining one is the live wire.
Some multimeters have a dedicated gear mark for testing live wires, which is "H". As long as the multimeter is turned to this gear, the black probe is suspended or wrapped around the finger, and the red probe is used to touch the wire to be measured. The one with the highest value displayed is the live wire, and the one with the lowest or no value displayed is the neutral and ground wires. If you wrap the black pen around your hand, the displayed numbers will be more sensitive.
