How to determine the zero wire and fire wire if you forget to bring a pen and only have a multimeter.
The limitations of electric pens are obvious, especially those with digital displays, which can sometimes make us misjudge. The light is too strong to read due to reflections, and the light is too dim for the numbers to be read even if they are too small. Too many numbers displayed, bright and dark, strong and weak, so you can not accurately judge the level of voltage. The sound and light sensor pen, only know whether there is electricity, but can not know what the voltage is. Neon bubble electric pens for outdoor testing, "you can only do it in the middle of the day, sooner or later, something is going to happen".
As an electrician, you can not have an electric pen, but you can not have a multimeter. The reason why a multimeter is called a multimeter is because it is powerful. A good multimeter, when we overhaul and repair can be half the effort.
A friend asked, there is no electric pen, how to use the multimeter to distinguish between zero and fire wire? For electricians, this is a kindergarten problem. Here is what I share.
First of all, determine whether your working environment has an earth wire, if there is an earth wire, it is very simple to operate.
1. When the power supply is three-phase, five-wire, we set the multimeter to the highest level of the AC voltage gear, respectively, to test the voltage between the five lines. Between the two lines of the voltage of 380 two are fire, the voltage of 220 a fire, a zero line, the voltage is zero or very small, a zero line, a ground.
2. power for single-phase three-wire, the multimeter to 220V AC gear, respectively, to test the voltage between each two lines. No voltage or voltage is very small two lines are zero and ground, the remaining one is the fire wire.
If there is no ground, to distinguish between zero and fire wire how to operate?
Some multimeters have an "H" marking for testing the fire wire. Simply set the multimeter to this marking, leave the black pen hanging in the air or wrap your fingers around it, and touch the wire you want to measure with the red pen; the one that displays a large value is the fire wire, and the one that displays a smaller value or no value at all is the zero wire and the earth wire. If you wrap the black pen around your hand, the display will be more sensitive.
