How to use a multimeter to determine short circuit, open circuit and leakage
Multimeter determines short circuit (220V circuit as an example)
(1): Disconnect circuit power.
(2): Cut off the circuit breakers of each branch of the circuit
Purpose: To eliminate the impact of branch roads on main roads.
(3): Measure the resistance between the live and zero lines of the main circuit. If the resistance value is 0, a short circuit (metallic short circuit) occurs in the main circuit.
Note: After confirming that there is a short circuit on the main circuit, continue to measure the resistance between the terminals of other devices on the main circuit. Identify the short circuit points in turn.
(4): Follow the same method as the main circuit to find whether there are short circuit points in each branch.
Note: The short circuit fault point of the circuit is difficult to determine, but as long as we follow the circuit drawing,
Divide the circuit into small pieces according to the main and branch circuits, patiently measure the resistance value, and everything will be solved easily.
3: Multimeter determines circuit breakage (220V circuit as an example)
The circuit break judgment can be judged based on the infinite resistance when the circuit is broken.
But when the circuit is more complex, we can turn on the power,
Then determine the abnormal points (such as the indicator light not lighting up, or other equipment working abnormally),
According to the circuit drawing, measure the voltage to ground step by step.
When the voltage of a component to ground is 0, it means there is an open circuit before it, so continue searching upward.
until the breaking point is determined.
4: Use a multimeter to determine leakage (220V circuit as an example)
How to judge when the shell is charged:
Turn on the power supply of the equipment, switch the multimeter to the AC voltage measurement mode, connect one end of the two test leads to the equipment shell, and the other end to ground, and measure the voltage between the shell and the ground. If voltage is present, the case is leaking.
How to judge when the line is leaking:
Since a multimeter needs to connect the test leads in series to the circuit when measuring current, which is troublesome, so if conditions permit, we can use a clamp ammeter to measure the circuit current.
Turn on the power supply of the circuit and pass the neutral and live wires of the main line through the clamp ammeter side by side. If there is no leakage, the current will be zero. If there is leakage, the current is not 0.
Divide the circuit into several sections and measure each section. Until the leakage point is determined.
