How to use a multimeter to check for open circuits and short circuits
1) It is an open circuit, and the small number showing 0 o'clock is a short circuit.
Do not use a multimeter to measure leakage. The power supply of a multimeter is usually a 9V battery. No leakage at low voltage does not mean no leakage at 220 high voltage. Use a megometer with at least 500V to measure. The two clamps of the megometer are connected to the two ends of the line and shake. handle, if the meter pointer moves toward zero, it is a leakage.
The three elements of a circuit are power supply, load, and intermediate links. The power supply is a device that provides electrical energy to the load. The load is a device that obtains electrical energy and converts it into other forms of energy. The switch in the intermediate link is to connect or disconnect the circuit, and the wire is to transmit the electrical energy.
Simply put, a short circuit is a lack of load, with only two elements: power supply and intermediate links. The open circuit lacks an intermediate link and only has two elements: power supply and load. For example, 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 insulation layer or other reasons. For some reason, there is a certain potential difference between the connected equipment and the earth, which is leakage. Therefore, leakage may occur in the power supply device, in the load, or in intermediate links.
Multimeter to check short circuit, open circuit and leakage
Use the resistance check method to check for short circuit and open circuit faults or use the buzzer gear to check for short circuit and open circuit faults.
When using a multimeter to check for short circuits and open circuits, and when using the resistance detection method, make sure the circuit power is cut off. When checking the load or line, select the appropriate resistance level. It is found that the reading of the multimeter is zero. If the multimeter is turned down, the reading is still zero. There must be a short circuit. It is found that the reading shows the overflow symbol "1". After adjusting the resistance level upward, the overflow symbol "1" is still displayed, which means there must be an open circuit. Use the buzzer setting of the multimeter to check for short circuits and open circuits. The prerequisite is to cut off the circuit power. During the detection, it was found If the multimeter beeps, it must be a short circuit. If the overflow symbol 1 is displayed, it does not necessarily mean that there is an open circuit. At this time, use the high resistance setting of the multimeter to continue measuring. If the overflow symbol 1 is still displayed, it means there is an open circuit.
Multimeter to check for 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, intermediate link or other reasons, the above three elements will have a potential difference with the earth. If you use a test pen to detect it, the neon tube will definitely continue to glow. When checking with a multimeter, one of the test leads is connected to the metal casing of the power supply device or equipment casing, etc., and the other test lead is connected to the earth. There is a voltage between them. The size of the multimeter reading indicates whether the leakage current leakage of one of the three elements: load, intermediate link, and power supply device is serious.
Among them, the best one is to measure leakage. At this time, look for a good grounding point at the detected location, such as a well pipe, moist earth, etc. Then connect one of the test leads of the multimeter to the shell of the charged body being tested, and connect the other test lead to the selected ground point. In this way, the leakage effect of detection is more obvious.
