How to use a multimeter to test the quality of the ground wire of the socket in your home
We don't have a professional ground resistance tester at home - it's not worth buying one just for this purpose, so there's no way to know the specific grounding quality of the ground wire. But you can still use simple measurements to determine whether the ground wire is grounded, or whether the ground wire is disconnected in the middle.
Multimeter test
Adjust the multimeter to 250V~ or the closest AC voltage range greater than 220V, and measure the voltage between the live wire and the neutral wire, and the live wire and the ground wire respectively.
If the difference between the two voltages is less than 5V, it proves that the ground wire is well grounded - and the smaller the difference, the better the grounding quality.
Bulb test
Take a light bulb, connect one end to the live wire, the other end to the neutral wire and the ground wire respectively, compare the brightness of the two bulbs.
If the brightness is the same twice, or the bulb is slightly dim when connected to the ground wire, the ground wire is well connected; if the bulb does not light up when connected to the ground wire, the ground wire is faulty.
Note: When testing with this method, there must be no leakage switch in the line, otherwise the leakage switch will trip when testing the ground wire, making comparison impossible.
phase detector
It is also very convenient to use. Plug it directly into the socket, observe the sequence of the three lights on the detector, and compare it with the example to know whether the ground wire is normal (the fault of the zero live wire can also be detected) - of course, it is the same as the first two. The method is the same, but you can still only know whether it is grounded, but the specific grounding quality cannot be known.
1 A good ground wire has a resistance value of about 4 ohms.
2. First, try pressing the leaky fuse test jump button to see if the leakage fuse is working.
3. When the power is on, I use a pointer multimeter to measure the voltage difference between the zero line and the ground line. Only when the meter is adjusted to the converter 10V range, I can measure a voltage of 3 to 5V. Therefore, to measure whether the ground wire is well connected to the ground, you can use a multimeter to test these two wires. If there is no small voltage, it means that the ground wire is open.
4. There are metal water pipes in the ground at home. After turning off the power, use the ohm setting of the multimeter to measure the resistance between the neutral wire and the ground wire. Because the water pipes in each house are different in age, the resistance value is also different, but the resistance between it and the ground wire is different. The resistance value can be used within 6 ohms. Measuring the resistance of the neutral wire and the ground wire when there is no power can best reflect whether the ground wire is qualified. The greater the resistance, the less safe it is!
5. Set the multimeter to the 50mA current setting. When closing the circuit and powering on, connect one of the two test leads of the multimeter to the neutral wire and touch the other to the ground wire. If it trips instantly, it means the grounding is good.
Because the minimum sensitivity of the leakage protection is 15mA, if it can trip in this small range and enter the ground from the zero line, it means that the ground wire in the home is qualified.
