Pointer type multimeter to distinguish between fire and neutral Turn the digital multimeter to the AC 20V gear (or AC 2V gear), remove the black test pen, insert the black test pen into the V/Ω jack, hold the insulating pen of the red test pen in one hand, and touch the two jacks in turn with the tip of the watch. The larger the displayed value is the live line, as shown. 2 Non-contact measurement method Sometimes, you need to find the fire line from the outdoor lighting line; at this time, you don't need to strip the insulation of the wire, use the red test pen to touch the insulation skin of the two wires in turn, the larger the reading is the fire line; Inductive voltage, so the range is best to choose AC 2V. 3.2v12-30Ah Lithium Battery Cells 3.2v12-30Ah Lithium Battery Cells,3.2v12-30Ah Lithium Battery Cells price,3.2v12-30Ah Lithium Battery Cells product Jiangsu Zhitai New Energy Technology Co.,Ltd , https://www.zt-tek.com
1 Contact measurement method The multimeter switch is placed in AC 250V or 500V, the first meter is connected to one end of the power supply, and the second meter is connected to the ground (such as water pipes, radiators, etc. or wet ground). If the grounding is good, when the multimeter reads about 220V, the first meter is connected to the live line of the power supply, as shown in Figure a. If the pointer does not move, the first meter is connected to the neutral line of the power supply. Even if the grounding resistance of the second test lead is large, the pointer will have a significant deflection when the first test lead is connected to the live line. 
Non-contact measurement method, the multimeter switch is placed in the AC 250V or 500V gear, the first test pen is connected to either end of the power supply, the second test pen is suspended on the table, and the insulating rod portion of the second test pen is held by hand ( Be careful not to touch the conductive part). If the first meter is connected to a live line, the head pointer can generally be deflected by 2 to 10 grids, as shown in Figure (b). The higher the sensitivity of the multimeter, the more pronounced the deflection. If the first line is connected to the zero line, the head pointer will not deflect.
[Important reminder] This method is applicable to any type of multimeter. This method does not pose a danger to the human body. Because the internal resistance of the pointer multimeter is 20K / V, if it is used to measure 220V voltage, the internal resistance of the pointer meter is 20K × 220V = 4400, which is safer.
3 pointer type multimeter to distinguish between the fire line and the zero line Note with the pointer type multimeter to distinguish between the fire line and the zero line must pay attention to safety. Specifically, the insulation of the test leads should be good, and the operator's hands and any part of the body should not be in direct contact with the metal parts of the test leads to avoid the risk of electric shock.
Digital multimeter distinguishes between the live and the neutral. We know that the digital multimeter's AC voltage is very sensitive. Even if a weak voltage signal is sensed, it can be displayed from the LCD screen. Using the ACV of the digital multimeter, use the inductive method to find The live line of AC power is intuitive, fast, accurate and safe.
1 contact measurement method 
3 pointer type multimeter to distinguish between the fire line and the zero line Note with the pointer type multimeter to distinguish between the fire line and the zero line must pay attention to safety. Specifically, the insulation of the test leads should be good, and the operator's hands and any part of the body should not be in direct contact with the metal parts of the test leads to avoid the risk of electric shock.
When the multimeter detects the lighting circuit and the device, it generally uses electricity to block the on/off condition of the measurement line, the initial measurement line and the insulation condition of the device; and the AC voltage block to measure whether the line or the device has voltage and voltage is normal. . 1 Electrical barrier to measure the resistance value of the line Electrical lines and various electrical related circuits can be measured using a multimeter electrical barrier. Because the resistance test is safe, convenient, and easy to be, it is highly praised by the circuit design and maintenance personnel. By testing the resistance value of the line, it is determined whether the line is open or shorted; by comparing the normal resistance value of the component with the resistance value at the time of failure, the quality of the component is determined. When testing the resistance of the lighting circuit and device, the device under test should be removed from the power supply and then tested. 2 Multimeter to detect short circuit fault of lighting circuit Fault phenomenon and cause When the lighting line is short circuited, the line current is very large, the fuse is quickly blown, and the circuit is cut off. If the fuse selection is too thick, it will burn the wire and even cause a fire.
The possible cause of the short circuit of the lighting line is incorrect wiring, the phase line is in contact with the neutral line; the insulation of the wire is damaged, the wire is touched or grounded at the damaged place; the inside of the electric appliance is damaged; the internal part of the lamp head is loose, causing the metal piece to be short-circuited, and the lamp head is filled with water. Wait.
The multimeter finds the fault phenomenon of the short circuit of the short circuit fault lighting line, but it is more complicated to determine the fault occurrence. We can use the electric resistance method to check the fault.
The electric resistance method is a method of judging the short-circuited portion by using the electric resistance of the multimeter and measuring the resistance value between the wires or the electrical appliance. After a short circuit occurs, disconnect the knife switch (or circuit breaker) on the power distribution board, and unplug all the electrical plugs, and turn off the power. Use a multimeter to place the R × 100 block and measure the resistance values ​​of the phase and neutral lines. If the pointer tends to zero (or deflect), the line has a short circuit (or leakage). Check the trunk line and each branch line section by section, cut off a line if necessary, measure the resistance of the two lines, and determine the location of the fault.
[Important reminder] When repairing, you should first find out the short-circuit point, and use the multimeter's electrical block to perform circuit segmentation and sub-area inspection in case of power failure. Step by step from the load end to the front end to check whether the work is caused by the line or the component, you can judge it. After the short-circuit fault point is removed, the fuse that is connected to the grid is re-powered. The multimeter detects the open circuit fault of the lighting line and the cause of the fault. When the lighting circuit is open, the circuit has no voltage, the lighting is not bright, and the electrical appliance cannot work. The reasons are: fuse blowing, wire breakage, loose ends, and switch damage. 
When the open circuit fault repairing multimeter detects the open fault of the lighting line, in the case of disconnecting the power supply, the multimeter can be used to block the on/off condition of the measuring line; or in the case of power supply, the voltage of the line can be measured by the multimeter AC voltage block. Determine the point of failure.
The multimeter detects the leakage of the lighting line. The reason for the leakage of the lighting line is that the insulation of the wire or electrical equipment is damaged by external force. Second, the long-term operation of the line leads to deterioration of the insulation aging. Third, the line is affected by moisture or pollution, resulting in poor insulation.
The troubleshooting of the leakage fault first determines whether the leakage is indeed. The R×10k block of the pointer multimeter can be used to measure the size of the insulation resistance of the road, or the digital multimeter is placed in the AC current block (this is equivalent to an ammeter), connected in series on the main switch, all switches are turned on, and all loads are removed. Including the bulb).
If there is current, it indicates that there is leakage. After determining the line leakage, you can continue the inspection by following the steps below. (1) Judgment is the leakage between the phase line and the neutral line, or the leakage between the phase line and the earth, or both. The method is to cut off the neutral line. If the current meter indication is unchanged, it is the phase line and the earth leakage; if the current meter indicates zero, it is the leakage between the phase line and the zero line; if the ammeter indication becomes smaller but not zero, it is the phase line and zero. Leakage occurs between the line, the phase line and the earth. (2) Determine the leakage range. Remove the shunt fuse or open the circuit breaker. If the ammeter indication is unchanged, the bus leakage; if the ammeter indicates zero, it is shunt leakage; if the ammeter indication becomes smaller but not zero, it indicates bus or shunt There are leakages. (3) Find the leakage point. After the above inspection, the switch of the line lamp is disconnected in turn. When the switch is turned off, the current meter indicates zero return, then the branch line leaks; if it is smaller, the branch line leaks, and there is leakage elsewhere; If all the lamps and lanterns are turned off and the current meter indication is unchanged, the section of the trunk is leaking. By narrowing the scope of the accident in turn, it is possible to further check whether the joints of the section of the line and the places where the wires pass through the wall are leaking. After finding the leakage point, the leakage fault should be eliminated in time.
[Important reminder] Short circuit, open circuit and leakage of lighting line are the most common faults. Only when we conduct specific measurement and analysis can we find out the fault point accurately, identify the nature of the fault, and take effective measures to eliminate the fault as soon as possible.