How can I tell if a wire is grounded or shorted with a multimeter?
If you want to check whether there is a short circuit in the line. First of all, the line should be powered off, and then each load switch should be opened, and the resistance between the two lines should be blocked by the ohm of the multimeter. Normally, the higher the resistance, the better. If you judge whether the line is grounded or not, you can use the ohm block of the multimeter. To measure the resistance of each line to ground. Also the bigger the better. It should be pointed out that it is not accurate to use a multimeter to measure whether there is a short circuit and grounding in the line. It should not be, if the grounding or short circuit resistance is very small, it can be detected with a multimeter, if the resistance is slightly larger. A multimeter cannot check it out, it is in the 380V low-voltage circuit. Measurements should be made with a 500V megger, either between lines or to ground. Both should be above 0.38 megohms. Otherwise it is unqualified.
First of all, you need to separate the live wire and neutral wire.
Ground wire: Turn the multimeter to the AC voltage range, and the range is higher than 220V. Insert the red test lead into the voltage hole, leave the black test lead unplugged, then insert the red test lead into one of the jacks of the socket, and observe the reading.
The one with the largest reading is the live wire, the one with the smaller reading is the zero wire, and the one with basically no moving reading is the ground wire.
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.
Turn the multimeter to the "short circuit" test function (if there is no resistance test), connect the red and black test leads to the ground of the circuit and the ground of the mains respectively. If the test result is a short circuit or the resistance is very small, the line is grounded. , and vice versa.
Check the leakage and grounding, and turn the multimeter to 200M. For example, to measure the insulation of equipment, connect one end of the test lead to the equipment shell or the ground wire, and the other end of the test lead to the line. When measuring insulation, hands should not touch the test leads to prevent measurement errors.
Adjust the resistance of the multimeter to 20K or 200K, turn off the main power supply and the load power supply, use a multimeter to connect a test lead to the live wire and a test lead to the ground wire to check the resistance value, then connect a test lead to the neutral wire and a test lead to the ground wire, and watch In the case of two resistance values, if there is one time above 7.3, or above 14., it means that the one with resistance value is connected to the live wire or neutral wire for leakage.
Many electricians will tell you to cut off all the power, measure the resistance between the two wires with the smallest resistance file (or use a diode file), and see if it is close to 0 ohms (or the diode file shows 0), if it is close to 0, Basically, it can be judged that the two wires are shorted together, and measure this wire to the ground to see if it is the same situation. If it proves that this wire is grounded, this method is of course feasible, but it is only in actual work It is inconvenient to cut off the power in many places. Is it feasible to measure without interruption?
