How to check circuit leakage with a multimeter
A multimeter has a buzzing mode, which means that if the same wire is short circuited with two probes, there will be no response. If it is a circuit, there will be a buzzing sound. Sometimes, when the device itself is poorly grounded and the shell is charged, a multimeter can be used. The red probe is placed on the shell, and the black probe is directly in contact with the ground. This can measure the strength of the shell leakage current and make it known in the remaining work. Similarly, it can be connected in series to the circuit to measure AC and DC currents.
To check for circuit leakage, a megohmmeter (shaker) should be used because the multimeter voltage is lower (9V) and the megohmmeter voltage is higher (500V). Because the operating voltage of the circuit is 220V, it is difficult to diagnose circuits with unclear leakage. To check the leakage of a circuit with a digital meter, the power supply needs to be cut off first. After discharging the circuit, measure it with resistance mode and 2M mode. The normal display is 1 (infinite).
Measure whether the circuit is in a connected state by using a multimeter in the ohm range. When measuring, choose the range where the meter pointer is close to deflection of 0 ohms. If the circuit is in a circuit, connect one end (A end) of the circuit to the 100 ohm range of a multimeter (red probe), and connect the black probe to the other end (B end) of the circuit to be measured. If the measured result is zero, it means that the circuit is connected, also known as a path. Only a path allows current to pass through the circuit; If the multimeter ohm range pointer at the A to B end of the line does not approach zero ohms, then the line is already in an open circuit state, and disconnection is called a circuit break or an open circuit.
A multimeter can easily identify the cause of electrical leakage.
Fault finding and analysis
First, inquire about the fault symptoms and obvious features of the user who reported the repair; Next, observe the surface for any obvious fault points, and then proceed to the next step of inspection.
1. First, disconnect the main isolation switch of the user's power supply line, and turn off all electrical loads of the user, such as unplugging the refrigerator plug, disconnecting the water pump switch, etc.
2. Place the gear of the digital multimeter in the 200M range of the ohm range, place one probe on one of the two output lines on the load side, and touch the other probe against the wall, preferably the grounding wire or temporary grounding wire. After the number displayed on the multimeter stabilizes, the insulation resistance value of the main circuit is read out. If the insulation resistance value is less than 0.5 megohms, then there is a problem with the main circuit. If the insulation resistance is above 0.5 megohms, then it can be ruled out that there is a problem with the main circuit. Measure another wire using the same method and check the value to see if there is a problem with the main circuit.
3. Check the insulation resistance values of the branches and various electrical appliances, and use the same method to detect them one by one until the fault point is found.
Operation precautions
When using the multimeter in the 200M ohm range, be careful not to touch the metal part of the probe with your hand during measurement, as this will result in inaccurate readings.
2. When measuring various electrical equipment, pay attention to discharging first to prevent capacitive currents in the equipment from injuring people.
