How to use a multimeter to check if a line is short-circuited or grounded?
If you want to check for a short circuit in the circuit. First, cut off the power supply to the line, then open the load switches and use the ohm range of the multimeter to measure the resistance between the two wires. Under normal circumstances, a higher resistance is better. If it is determined whether the circuit is grounded, the ohm range of the multimeter can be used. Measure the resistance of each circuit to ground. The bigger the better. It should be pointed out that using a multimeter to measure for short circuits and grounding in a circuit is inaccurate. It is also not appropriate. If the grounding or short-circuit resistance is very small, it can be detected with a multimeter. If the resistance is slightly larger, it should not be detected. A multimeter cannot detect it in a low voltage circuit of 380V. A 500V shaker should be used for measurement, whether between lines or to ground. All should be above 0.38 megaohms. Otherwise, it is unqualified.
Firstly, it is necessary to separate the live and neutral wires.
Ground wire: Set the multimeter to the AC voltage range, and the range should be higher than 220V. Insert the red probe into the voltage port, do not insert the black probe, and then insert the red probe into one of the sockets to observe the reading.
The line with the highest reading is the live line, the line with the lowest reading is the neutral line, and the line with almost no movement is the ground line.
If two readings are small and one reading is large, it means that the ground wire is not grounded and the ground wire is also connected to the neutral wire. The second step behind does not need to be measured.
Set the multimeter to the "short circuit" test function (if not available, it can be used for resistance testing). Connect the red and black probes to the ground of the circuit and the ground of the mains respectively. If the test result shows a short circuit or extremely low resistance, the circuit is grounded. Otherwise, it is not.
Check for leakage and grounding, and set the multimeter to 200M. For example, when measuring equipment insulation, connect one end of the probe to the equipment casing or ground wire, and the other end of the probe to the circuit. When measuring insulation, hands should not touch the probe to prevent measurement errors.
Set the resistance of the multimeter to 20K or 200K, turn off the main power and load power, use a multimeter to connect one probe to the live wire and one probe to the ground wire, check the resistance value, then connect one probe to the neutral wire and one probe to the ground wire, and observe the resistance value twice. If there is a resistance value of 7.3 or above, or 14 or above, it indicates that the live wire or neutral wire connected to the multimeter with a resistance value is leaking.
