To check if the circuit is shorted or grounded, how do I use a multimeter?
1) Turn off the power first, set the multimeter function switch to the buzzer mode, and place the two multimeter probes on the two terminals to be tested. If there is a short circuit, there will be a buzzing sound and a small conduction voltage value displayed. At this time, there is a short circuit between these two tested points.
2) Measuring the insulation of a circuit with a multimeter can determine if the circuit 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 determined that the phase line is grounded. If not grounded, the insulation value is very high. Measure the phase to phase insulation again. If the phase to phase insulation is zero, it indicates a short circuit between the two phases of the circuit.
3) Ensure that there is no power in the circuit, use the resistance mode (with the pointer meter in RX10 mode and the digital meter in on/off mode), and connect the two meter bars to the two points (or two wires) to be measured. If the pointer meter does not move, it is an open circuit, and if it is fully swung, it is a short circuit; The number on the digital meter remains unchanged and there is no sound when there is a short circuit. The short circuit will sound or the number will be zero.
4) Separate the cores of the two ends of the wire without touching each other, then turn the multimeter to the same position as above, and place the probes on two different colored wire ends. If the measured value is above 0.5 megohms or shows infinity, then the insulation of the circuit is not a problem, that is, there is no leakage in the circuit; If the measured value is below 0.5 megohms, then the insulation of the circuit is not qualified and there is leakage. Search for all the connectors and junction boxes in the circuit after this circuit breaker to see if the insulation of the connectors is not properly done. Then use resistance measurement method to check with a multimeter at each connector and junction box. The reason is that a high current will automatically trip the circuit breaker when a short circuit occurs, and the circuit will not burn out much. In general, the position of the short circuit can be determined by resistance measurement at the joint or junction box.
