How to Determine the Zero Line and Live Line of a Multimeter
The limitations of electric pens are obvious, especially those with digital displays, which sometimes make us misjudge. The light is too strong, and due to the reflection, it is difficult to see clearly. The light is too dim, and the numbers are too small to see clearly. The displayed numbers are too many, fluctuating in brightness, strength, and weakness, 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 determine the voltage. The neon bubble electric pen is being tested outdoors, "it can only be done at noon, something will happen sooner or later.
As an electrician, you can do without an electric pen, but you cannot do without a multimeter. The reason why a multimeter is called a multimeter is because of its powerful functions. A good multimeter can achieve twice the result with half the effort during our maintenance and repair.
A friend asked, how can a multimeter distinguish between zero and live wires without an electric pen? For electricians, this is a kindergarten problem. Here is my sharing.
Firstly, determine if your work environment has a ground wire. If there is a ground wire, the operation is very simple.
When the power supply is three-phase and five wire, we set the multimeter to the highest AC voltage range and test the voltage between the five wires separately. The two wires with a voltage of 380 are both live wires, the one with a voltage of 220 is live wire, the one with a voltage of zero or very low, the one with a voltage of zero and the one with a ground wire.
When the power supply is single-phase three wire, set the multimeter to AC 220V and test the voltage between each two wires separately. The two wires with no or very low voltage are the zero wire and the ground wire, and the remaining one is the live wire.
If there is no ground wire, how to distinguish between the zero wire and the live wire?
Some multimeters have a special gear mark for testing the live wire, which is "H". As long as the multimeter is set to this gear, the black lead is suspended or wrapped around the finger, and the red lead is used to touch the wire to be measured. The displayed value is the live wire with a large value, while the displayed value is the zero wire and the ground wire with a small or no value. If you wrap the black pen around your hand, the display of numbers will be more sensitive.
