How to detect short and broken circuits with a multimeter
Multimeter for engaged in electronics-related, electrician-related, maintenance-related friends, is the necessary "hard core" tools, very powerful, can be used to measure AC voltage, DC voltage, AC current, DC current, resistance, capacitance, diode, transistor, temperature and so on. For example, when we are testing and debugging products, we need to use the multimeter to help find problems.
When a product fails, I usually start by measuring the input and output voltages with the voltage gear to determine if the power supply part of the circuit is normal. Voltage is not normal, many times there is a short circuit or broken circuit.
Buzzer gear to measure short-circuit, disconnection
Digital multimeter generally have a buzzer file, measurement to connect will be "BI", "BI" ring, very intuitive, do not have to stare at the multimeter to see.
When measuring the two should not be connected to the position, if issued "BI", "BI" ring, indicating a short circuit; when measuring the two should be connected to the position, but did not issue "BI BI", "BI" ring, indicating a broken circuit;
If your multimeter does not have a buzzer file, you can also use the resistance file, in accordance with the method of measuring the resistance value to determine whether the short-circuit or disconnection, if the resistance becomes very small, only a few ohms, or even zero a few ohms, that means a short-circuit; if the measurement of the resistance value is not or the resistance value is quite large, then it means that the disconnection.
Remember to disconnect the power supply when measuring with buzzer or resistance!
Leakage measurement
Leakage is divided into strong leakage and weak leakage. Strong power leakage refers to AC high voltage leakage, this leakage will electrocute people or cause leakage switch tripped, you can play the multimeter to the AC file, measure whether there is a certain AC voltage. Another method is to disconnect the power supply, with the maximum range of the resistance file, measure the leakage point and the firewire (L) or zero line (N) between the resistance value, if no leakage, the resistance value is great, equivalent to insulation, if the resistance value to ground is not large enough to measure the resistance value of a few hundred K, then there may be leakage.
If you want to measure the weak circuit of the weak leakage, you can use the current file of the multimeter, the multimeter series series connection to the circuit to measure the working current increases. For example, the product is a normal standby current is tens of microamps, but measured hundreds of microamps, or even to a few milliamps to go, that the circuit has a leakage of components. Measure the current if you are not sure of the size of the working current, you can start with a larger range of gear, and then slowly reduce the range to test, over range is easy to burn the fuse of the multimeter.
