How to use a multimeter to measure short circuit, open circuit and leakage
Before confirming the test, the circuit must be in a power-off state, and it is strictly prohibited to operate with electricity, especially high-voltage electricity. If you are using an analog multimeter, you only need to set it to R×10. The digital multimeter will have a buzzer. You can use the buzzer setting directly or the resistance setting.
Pay attention to the insertion method of the test leads. The black test lead is inserted into the COM jack and the red test lead is inserted into the voltage measuring resistor jack. Place the test leads of the multimeter on both ends to be measured. If the test leads of the pointer multimeter do not move, it means that the resistance value is infinite, which is an open circuit state. The digital multimeter's circuit breaker status is that the buzzer does not sound, or the resistor level displays 1.
If the pointer of the analog multimeter is fully biased, the digital multimeter makes a beeping sound, or the resistance value displays zero or very small, it means there is a short circuit.
Leakage is the leakage of current due to insulation damage or other reasons. If there is a certain potential difference between the electrical shell and the mains live wire and the ground for some reason, leakage will occur.
Electrical appliance live measurement: Use a digital multimeter or pointer multimeter to measure, set the voltage to 250V AC, and pay attention to the positions of the red and black test leads. To measure the metal casing of the electrical appliance where leakage is suspected, connect one test lead to the casing of the electrical appliance and the other to ground (or faucet).
When the pointer or digital display voltage is higher than 30-50V, switch to the AC 50V range. If the power supply is confirmed to be higher than 30 volts, it is a leakage, and if it is lower than 30 volts, it is normal. Then swap the zero and fire power supply plug wires and measure again. Can be determined.
You can also use an electric meter pen. The best way to detect leakage is to use an electric pen to touch a charged object. If the neon bulb lights up and goes out immediately, it proves that the charged object is charged with static electricity. If it stays lit for a long time, it must be a leakage.
