Ingeniously use a multimeter to check the short circuit and grounding of the circuit

The meter is generally used to test whether the wires in the home are short-circuited, whether there will be leakage, or to test which wire has electricity.

If you want to check whether the circuit is short-circuited. First, power off the line, then open each load switch, and use the ohm of a multimeter to block the resistance between the two wires. Under normal circumstances, the larger the resistance, the better. If you judge whether the line is grounded, you can use the ohm block of a multimeter. To measure the resistance of each line to ground. The bigger the better. It should be pointed out that it is inaccurate to use a multimeter to measure whether the circuit is short-circuited and grounded. 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. The multimeter cannot be checked out, in the low-voltage circuit of 380V. It should be measured with a 500V shaker, whether it is between lines or to ground. All should be above 0.38 megohm. Otherwise it is unqualified.

First of all, the live wire and the neutral wire need to be separated.

Ground wire: Set the multimeter to the AC voltage range, and the range is higher than 220V. Insert the red test lead into the voltage hole and leave the black test lead unplugged, then insert the red test lead into one of the sockets and observe the reading.

The reading is the live wire, the smaller reading is the zero wire, and the reading basically unchanged 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 later does not need to be measured.

Set the multimeter to the "short circuit" test function, (if not, you can test the resistance), 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 extremely small, the circuit is grounded. , And not vice versa.

Check the leakage and grounding, and set the multimeter to 200M. For example, to measure the insulation of the equipment, connect one end of the test lead to the equipment case or the ground wire, and the other end of the test lead to the line. When measuring insulation, your 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 and load power, use a multimeter to connect one test lead to the live wire and one test lead grounding wire to check the resistance, then one test lead to the neutral wire and one test lead grounding wire to watch If the resistance value is higher than 7.3 or 14., it means that the live wire or neutral wire of the resistance value is leaking.

Many electrical labor unions tell you to cut off all the power, use the resistance file (or use the diode file) to measure the resistance between the two wires to see if it is close to 0 ohms (or the diode file shows 0). If it is close to 0, then Basically, it can be judged that the two wires are shorted and connected together. Also, measure this wire to the ground to see if the same situation is true. If it is proved that the wire is grounded, this method is of course feasible, but in actual work. It is inconvenient to cut off the power in many places. Is it feasible if the power is not measured?

Ingeniously use a multimeter to check the short circuit and grounding of the circuit

The essence of voltage is the potential difference. As long as the voltage between the two wires is 0, you can use the resistance profile to measure:

1. Suppose you want to measure whether there is a short circuit between line A and line B. There may be a voltage (for example, 220 volts) to the neutral line between line A and line B. The potentials on their lines are potential A and potential B, many What people think of is that if you use the resistance gear to measure directly, you must disconnect the power supply on line A and line B respectively before you can measure. This idea is not to say that it is wrong, it can only be said to be too conservative.

Use a multimeter to check the short circuit and grounding of the circuit

2. Set the multimeter directly to the AC voltage range, select the range, such as AC1000 volts, etc., and then use the AC voltage range of the multimeter to measure line A and line B. If there is a relatively high voltage between the two lines (such as 200 volts) ), it can be proved that the potential A and the potential B are not equal, that is to say, there is a voltage difference between the potential A and the potential B. The two wires are not equipotential, and the two wires are not shorted together.

Ingeniously use a multimeter to check the short circuit and grounding of the circuit

3. If there is no voltage between line A and line B in AC voltage measurement, for the sake of guarantee, choose a DC voltage file such as 1000 volts to measure between them, and confirm that there is no DC voltage. This can prove potential A and potential B. Equal, pay attention to it does not mean that they have no voltage to the neutral line N. For example, line A and line B are both 220 volts to the neutral line N, but the voltage between them is also 0 volts. At this time, you can use the resistance file to measure The resistance between these two wires is close. If it is close to 0 ohm, it means that the two wires are shorted together.

Ingeniously use a multimeter to check the short circuit and grounding of the circuit

4. As for whether the measurement is grounded, it is simple to use the above method to measure. The idea is to understand the ground wire as an ordinary wire. But in general to measure whether it touches the ground, you can use a shaker to measure the insulation resistance (the general insulation is 5 megohms). At this time, it is necessary to cut off the power to measure.