How to use a multimeter to detect short circuits in circuits
1) Turn off the power first, set the function switch of the multimeter to the buzzer position, and place the two test leads of the multimeter on the two terminals to be tested. If there is a short circuit, there will be a buzzer and a very small conduction voltage value will be displayed. At this time, there is a short circuit between the two measured points.
2) Use a multimeter to measure the line insulation to know whether the line is short-circuited. For example, when measuring the insulation of a single phase to ground, if the insulation value is zero (metallic grounding) or very low (non-metallic grounding), it can be judged that this phase line is grounded. If not grounded, the insulation value is very high. Then measure the phase-to-phase insulation. If the phase-to-phase insulation is zero, it means there is a short circuit between the two phase lines.
3) Make sure that there is no power in the line, use the resistance setting (the pointer meter is set to RX10, the digital meter has an on-off setting that will beep for a while), touch the two meter rods to the two points (or two lines) to be measured, and the pointer does not move. It is an open circuit, and if the full scale is exceeded, it is a short circuit; the digital meter's open circuit number does not change, and there is no sound, but the short circuit will beep, or the number is zero.
4) Separate the wire cores at the two ends of the wire without touching each other, then put the multimeter to the and above position, and place the test leads on the wires of two different colors. If the measured value is within 0.5 trillion If the value is above 0.5 ohms, or it displays infinity, then there is no problem with the insulation of the line, that is, there is no leakage in the line; if the measured value is below 0.5 megohms, then the line insulation is unqualified and there is leakage. Find all the joints and junction boxes in the line after this circuit breaker to see if the insulation of the joints is not good, and then check with a multimeter at each joint and junction box using the resistance measurement method. The reason is that a large current is generated at the moment of short circuit and the circuit breaker automatically trips. The circuit will not be burned much. Generally, the position of the short circuit can be determined by resistance measurement at the joint or junction box.
