How to distinguish between zero wire and live wire using a digital multimeter
1. First, check the multimeter to see if it is in good condition. Insert the black probe into the com end and the red probe into the v/R end, and prepare accordingly.
2. Set the gear to AC 500V, with the black probe grounded (or conductive object to the ground) and the red probe touching two wires respectively. It is found that the number on the meter has changed, indicating that the wire around 220V is a live wire and the other wire is a zero wire.
3. Wrap the wire of the black pen around your hand three times, remember not to touch the pen with your hand. The red pen contacts the two wires respectively, and the number on the watch that changes is a live wire and the other is a zero wire. (Small experience: In general, when one end of a digital meter is suspended and the other end comes into contact with a wire, there is a faint digital display indicating that it is a live wire. If not, it is a zero wire.)
In short, measuring the zero wire and the live wire is so easy. So, let's talk about how to distinguish the live wire, ground wire, and zero wire?
1. Set the digital multimeter to the AC voltage range of 500V, first connect one of the probes to ground, and then connect the other probe to one of the other wires. If the voltage displays around 180-230V, it is a live wire. Use this probe to measure the other wire, and if the voltage is around tens of volts, it is a zero wire. If there is only a few volts of variation or no change, this is the ground wire.
2. In terms of color, according to national regulations, yellow, green, and red are the phase lines, blue is the zero line, and yellow and green are the ground lines.
How to use a multimeter to measure cable break points
When there is a broken wire fault inside a cable or cable, the exact location of the broken wire is difficult to determine due to the wrapping of the external insulation skin. Using a digital multimeter can easily solve this problem.
Specific method: Connect one end of the broken wire (cable) to the live wire of 220V mains power, and suspend the other end in the air. Pull the digital multimeter to the AC2V position, starting from the live wire connection end of the wire (cable), hold the tip of the black probe with one hand, and slowly move the red probe along the insulation of the wire with the other hand. At this time, the voltage value displayed on the display screen is about 0.445V. When the red probe moves to a certain position, the voltage displayed on the display screen suddenly drops to a few tens of volts (about one tenth of the original voltage), and about 15cm forward (from the end of the live wire connection) from that position is where the wire (cable) breakpoint is located.
When using this method to check the shielding wire, if only the core wire is broken and the shielding layer is not broken, then this method is powerless.
