Methods of Using a Multimeter to Determine Short Circuits, Open Circuits and Leakage Currents
The methods of using a multimeter to determine short - circuits, open - circuits, and leakage currents are as follows:
Short - circuit: Disconnect the power supply and measure the resistance. When the resistance is very small or even zero, it indicates a short - circuit (metallic short - circuit).
Open - circuit: Disconnect the power supply and measure the resistance. When the resistance is infinite, it indicates an open - circuit.
Leakage current: Connect the power supply. Measure the voltage between the device's outer shell and the ground. A relatively large voltage value indicates a leakage current. Also, measure the difference in the currents flowing through the live wire and the neutral wire. If the difference is not zero, there is a leakage current.
The above is the principle of using a multimeter to judge circuit faults. However, in the actual process of judging circuit faults, there are some differences.
Next, let's take a look at how to use a multimeter to determine short - circuits, open - circuits, and leakage currents in an actual circuit.
1. Summary
The following picture shows the methods I've summarized for using a multimeter to detect short - circuits, open - circuits, and leakage currents. You can save it for future reference.
2. Using a multimeter to determine short - circuits (taking a 220V circuit as an example)
(1) Disconnect the circuit power supply.
(2) Switch off the circuit breakers of each branch of the circuit.
Purpose: To eliminate the influence of the branches on the main circuit.
(3) Measure the resistance between the live wire and the neutral wire of the main circuit. If the resistance value is zero, a short - circuit (metallic short - circuit) has occurred in the main circuit.
Note: After determining that there is a short - circuit in the main circuit, continue to measure the resistance values between the wiring terminals of other devices on the main circuit. Determine the short - circuit point one by one.
(4) Follow the same method as for the main circuit to check whether there are short - circuit points in each branch.
Note: It is relatively difficult to determine the short - circuit fault point in a circuit. However, as long as we divide the circuit into small parts according to the main circuit and branches based on the circuit diagram and patiently measure the resistance values, all problems can be solved.
