To check if a wire is shorted or grounded, how do I use a multimeter?
If you want to check the line for shorts. Firstly, you have to de-energise the line, then pull the individual load switches apart and use the ohm stop of your multimeter for the resistance between the two two wires. Under normal circumstances, the higher the resistance, the better. If you judge whether the line is grounded or not, you can use the ohm stop of the multimeter. to measure the resistance of each wire to ground. Also the larger the better. It should be noted that the use of a multimeter to measure the line with or without a short circuit and grounding is not accurate. Should not be, if the ground or short circuit resistance is very small, then the multimeter can be detected, if the resistance is slightly larger. Multimeter is not checked, in the 380V low voltage circuit. Should be measured with a 500V swing meter, whether between the lines or to ground. Should be above 0.38 megohm. Otherwise it is unqualified.
First of all, you need to separate the fire line and zero line.
Ground: Turn the multimeter to the AC voltage gear, and the gear is higher than 220 V. Insert the red pen into the voltage hole, the black pen is not inserted, and then use the red pen to insert into one of the jacks of the socket and observe the reading.
The largest reading is for the firewire, smaller readings for the zero line, readings basically did not move for the ground line.
If there are 2 readings of small, a reading of large that the earth wire is not grounded, the earth wire is also connected to the zero wire. The second step behind does not need to be measured.
Multimeter to "short circuit" test function, (if not you can play to the resistance test), the red and black pens were connected to the circuit of the ground and utility ground, if the test results for the short circuit, or resistance is very small, the line is grounded, and vice versa, there is not.
To check for leakage and grounding, hit the multimeter on 200M. For example, to measure the insulation of equipment, connect one end of the meter pen to the equipment housing or ground, and the other end of the meter pen to the line. When measuring insulation, the hand should not touch the pen to prevent causing measurement errors.
Multimeter resistance gear to 20K or 200K, turn off the main power supply and load power, with a multimeter pen connected to the firewire, a pen ground line, check the resistance value, and then a pen connected to the zero line, a pen ground line, watch the two resistance situation, if there is a time to appear more than 7.3, or more than 14.1, indicating that there is resistance value of a time to connect to the firewire or zero line leakage.
The essence of voltage is the potential difference, as long as the voltage between the two lines is 0, you can use the resistance file measurement:
1, assuming that to measure whether there is a short circuit between line A and line B, line A and line B between the zero line may have a voltage (for example, there are 220 volts), they are on the line of potential for the potential A and potential B, the first thing that many people think of is that, if the direct measurement of the resistance file, must be disconnected from the power supply on the line A and line B, and then can be measured, this line of thought is not to say that the error, can only say that it is too conservative.
2, directly to the multimeter dial to AC voltage gear, select the highest range, such as AC1000 volts, and then use the multimeter AC voltage gear to measure the line A and line B, if there is a relatively high voltage between the two lines (for example, 200 volts), it can be proved that the potential A and potential B is not equal, that is, there is a difference in voltage between the potential A and the potential B, these two lines are not equipotential, these two lines are not shorted together.
3, if the line A and line B using AC voltage measurement of no voltage, in order to ensure that, and then choose a DC voltage file, such as 1000 volts to measure between them, to confirm that there is no DC voltage, this kind of proof of potential A and potential B is equal, pay attention to equal does not mean that they have no voltage on the zero line N Oh, for example, the line A and line B on the zero line N are 220 volts, but the voltage between them is also 0 volts, this time, you can use the smallest resistance gear to measure the resistance between the two lines, if close to 0 ohms, that the two lines are shorted together.
4, as for the measurement of whether the ground, simple can also be used to measure the method above, the idea is to take the ground as an ordinary line to understand. But the general measurement of whether to touch the ground, you can use a shaking table to measure the insulation resistance (generally insulated with 5 megohms), this time it is necessary to power off to measure.
