How to use a multimeter to judge the breakpoint of the internal break of the wire
Due to the manufacturing process or external force, the wires sometimes break internally. When the wire breaks internally, how to quickly judge the break point with a multimeter? Two methods can be used: measuring resistance or measuring voltage.
The two ends of a section of wire are respectively terminal A and terminal B, and point O is the midpoint of this section of wire. We can first use the ohm gear of the multimeter to measure whether point A and point O are connected. If they are connected, it means that the fault point is in the section O~B. If it is not turned on, it means that there is a fault point in the A~O segment. Determine which half section the fault point is in, and then use this method to gradually narrow down the range until the fault point is found.
In this way, the test leads of the multimeter may not be long enough and can be extended with other wires. You can also add a voltage of 220 volts to the A terminal, and measure the voltage to ground with the AC voltage range of the multimeter at the O point. If the voltage is normal, it means that the fault is in the O~B section. The specific measurement method is the same as the resistance measurement method. This method does not need to extend the test leads of the multimeter, but the live measurement must pay attention to safety.
For stranded wires, twist several wires together at one end first.
A, B, and C are three wires wrapped in the same insulator, and one of them is broken. Let's connect a section of the wire first. Then use the ohm range of the multimeter to measure the three points A, B, and C respectively. If A and B are connected, A and C are not connected, and B and C are not connected, then the broken line must be on the C wire. The same method can also be used to determine which wire the fault point is on.
Of course, the voltage method can also be used to measure. Connect the connected end to 220 volts, and then use a multimeter to measure the ground voltage at points A, B, and C. If there is no or abnormal ground voltage at any point, it will indicate which wire the fault is on. . Determine which wire the fault point is on, and then use the "half section" rule mentioned above to gradually investigate.
The half-section method needs to destroy the insulation of the wire to check the fault point of the wire. A little work experience is for reference only. Now there is a special cable breakpoint detection instrument, but it may be more expensive, I have not used it.
