How to use a multimeter to check open circuit and short circuit
First connect the test leads, the choice of the multimeter can be a pointer or a digital display, the red test lead is inserted into the VΩ file, and the black test lead is inserted into the COM terminal to ensure that the multimeter is normal; rotate the multimeter gear, and use the resistance file to measure short circuit or open circuit, such as 200Ω file; connect the test leads to both ends of the line, if the multimeter does not display (display 1), it means an open circuit, and if it displays a small number at 0 o'clock, it means a short circuit.
Do not use a multimeter to measure the leakage. The power supply of the multimeter is generally a 9V battery. Low voltage does not mean that 220 high voltage does not leak. It must be measured with a shaker of at least 500V. The two clamps of the shaker are connected to the 2 ends of the line. Handle, the pointer of the meter head runs to the zero direction, which is leakage.
The three elements of circuit composition are power supply, load, and intermediate link. The power supply is a device that provides electric energy to the load, and the load is a device that obtains electric energy and converts it into other forms of energy. The switch in the middle link is to turn on or off the circuit, and the wire transmits electric energy.
Simply put, a short circuit is a lack of load, and there are only two elements, the power supply and the intermediate link. The open circuit lacks an intermediate link, only two elements of power supply and load, such as the switch is not closed and the wire is disconnected. Leakage is the current leakage of live equipment or devices due to the aging of the insulating layer or other reasons. For some reason, there is a certain potential difference between the ground and the ground, which is leakage. Therefore, leakage may occur in the power supply device, the load, or the intermediate link.
Multimeter check short circuit, open circuit, leakage
Check short-circuit and open-circuit faults with the resistance test method or check short-circuit and open-circuit faults with the buzzer gear.
When using a multimeter to check for short circuits and open circuits, use the resistance detection method to determine whether the circuit power is cut off. When checking the load or line, select the appropriate resistance gear. It is found that the reading of the multimeter is zero, and the gear of the multimeter is lowered. If the reading is still zero, there must be a short circuit. It is found that the reading shows the overflow symbol "1", and the overflow symbol "1" is still displayed after the resistance gear is adjusted upwards. There must be an open circuit. Check the short circuit and open circuit with the buzzer gear of the multimeter, and the premise is to cut off the circuit power supply. During the test, it was found The multimeter beeps, it must be a short circuit. If the overflow symbol 1 is displayed, it is not necessarily an open circuit. At this time, continue to measure with the high resistance gear of the multimeter. If the overflow symbol 1 is still displayed, it means that there is an open circuit.
Multimeter to check leakage
According to the description of leakage, it can be seen that due to the aging of the insulation layer of the load, power supply device, and intermediate links or other reasons, there will be a potential difference between the above three elements and the earth. If it is detected with a test pencil, its neon tube will definitely continue to glow. When checking with a multimeter, one of the test leads is connected to the metal casing or equipment casing of the power supply unit, and the other test lead is connected to the ground, and there is voltage between them. The reading of the multimeter shows whether the leakage current leakage of one of the three elements of the load, the intermediate link, and the power supply device is serious.
Among them, the effect of measuring leakage is the best. At this time, look for a good grounding point at the detected position, such as well pipes, wet ground and other good grounding points. Then connect one of the test leads of the multimeter to the shell of the charged body to be detected, and the other test lead to the selected grounding point. In this way, the leakage effect of detection is more obvious.
