How to use a multimeter to test the earth wire of your home outlet
We don't have a professional earth resistance tester in our house - and it's not worth getting one specifically for this purpose - so there's no way to know the exact quality of the earth's ground. But it's still possible to tell if the ground is grounded, or if it's disconnected in the middle, with a simple measurement.
Multimeter test
Multimeter set to 250V ~ or the closest and greater than 220V AC voltage gear, respectively, to measure the voltage between the fire wire and the zero line, fire wire and ground.
If the difference between the two voltages is less than 5V, it proves that the ground is well grounded - and the smaller the difference, the better the grounding quality.
Light bulb test
Take a light bulb, one end is connected to the fire wire, the other end is connected to the zero wire and the earth wire, and compare the brightness of the bulb twice.
If the brightness of the two times the same, or connected to the ground when the bulb is slightly dark, then the ground is well grounded; if connected to the ground when the bulb is not bright, then the ground fault.
Note: When testing this method, there can be no leakage switch in the line, otherwise the leakage switch will trip when testing the ground and no comparison can be made.
Phase Detector
This thing is cheaper than a multimeter, about 10 yuan, many brands have, the average user family should always have.
It is also quite convenient to use, plugged directly into the socket, observe the order of the three lights on the detector, against the example, you can know whether the ground is normal (zero fire fault can also be detected) - of course, and the first two methods, still only know whether the ground, the specific quality of the ground, there is no way to know.
1, a good earth wire its resistance value of about 4 ohms,
2, first of all, try to press the leakage insurance test jump button, to see if the leakage insurance device spirit.
3, in the case of power, I used a pointer multimeter to measure the voltage difference between the zero line and the ground line, only to adjust the meter to the variable current 10V gear, measured to have 3 to 5V voltage. So, to measure whether the earth wire into the ground is good, the multimeter can be used to test these two lines, if there is no small voltage, indicating that the earth wire is disconnected.
4, the home has a metal water pipe into the ground, after turning off the power, using the multimeter ohm file to measure the resistance between the zero line and the ground line, because the water pipe of each home is not new or old, and its resistance value is also different, but the amount of resistance between it and the ground line within 6 ohms can be used. In the absence of electricity to measure the resistance of the zero line and the ground line can best reflect whether the ground line is qualified, the larger the resistance the more unsafe!
5, the multimeter to the current 50mA gear, in the closing of the power, with the two pens of the multimeter, one end of the zero line, one end of the touch ground, can instantly trip that is a good grounding.
Because the minimum sensitivity of the leakage insurance in 15mA, if you can trip in this small range, and from the zero line into the ground, that is, the ground for the home qualified.
