Multimeters for short-circuit, open-circuit and leakage test methods
Multimeter judgement of short circuit, broken circuit, leakage method is.
Short circuit: disconnect the power supply, measure the resistance, resistance is very small or even 0 when it is a short circuit (metallic short circuit).
Disconnect: disconnect the power supply, measure the resistance, the resistance is infinity when it is disconnected (open circuit).
Leakage: Turn on the power supply, measure the shell voltage to ground, the voltage value is larger for the leakage; measure the difference between the current flowing through the fire line and the zero line, not 0 is leakage.
Above is the multimeter to determine the principle of circuit failure, however, in the actual circuit fault judgement, there are some different points.
Next, we look at the actual circuit how to use the multimeter for circuit short-circuit, disconnection, leakage judgement.
1: Summary
The picture below is my summary of the multimeter to check the short circuit, broken circuit, leakage method, you can save it for future use.
2:Multimeter judgement short circuit (220V circuit for example)
(1):Disconnect the circuit power.
(2): cut off the circuit of each branch circuit breaker
Purpose: to exclude the branch circuit on the dry circuit.
(3): Measure the dry circuit resistance between the fire line zero line, if the resistance value is 0, the dry circuit in the short circuit (metal Xing short circuit).
Note: When it is determined that there is a short circuit in the dry circuit, continue to measure the resistance between the terminals of other equipment on the dry circuit. Sequentially determine the short-circuit point.
(4): In accordance with the same method as the main circuit, to find the branch circuit whether there is a short-circuit point.
Note: the circuit of the short-circuit failure point is more difficult to determine, but as long as we are based on circuit drawings.
The circuit based on the trunk branch circuit divided into small pieces, patiently measure the resistance value, everything can be solved.
3: multimeter judgement break (220V circuit as an example)
Break judgement can be based on the break resistance to infinity to judge, but when the circuit is more complicated, we can not judge the resistance of the circuit.
But when the circuit is more complex, we can turn on the power.
Then determine the point of abnormality (such as indicator lights do not light up, or other equipment working abnormally).
According to the circuit drawings, step by step measurement of the voltage to ground.
When a component of the ground voltage is 0, that there is a circuit breaker before it, continue to look up.
Until the point of disconnection is determined.
