The multimeter detects the open circuit fault of the lighting circuit
1. Fault phenomenon and cause
When the lighting circuit is open, there will be no voltage in the circuit, the lighting will not light up, and the electrical appliances will not work. The reasons are: the fuse is blown, the wire is broken, the wire end is loose, the switch is damaged, etc.
2. Overhaul of open circuit faults
When the multimeter detects the open circuit fault of the lighting line, in the case of disconnecting the power supply, the multimeter can be used to block the continuity of the measurement line; or in the case of power on, the multimeter can be used to measure the voltage of the line with AC voltage to determine the fault point.
The open circuit fault of the lighting circuit can be divided into three situations: total open circuit, partial open circuit and individual open circuit.
(1) All open circuits.
This type of fault mainly occurs on the main line, in the power distribution and metering devices, and within the scope of the household devices. Usually, the connection of each joint of the above-mentioned parts (including the melt terminal) should be checked in turn. Generally, the failure of the wire head to break away from the connection is the most common; secondly, check the opening and closing of the dynamic and static contacts of each line switch .
(2) Partial open circuit.
This type of fault mainly occurs within the range of branch lines. Generally, check the connection of each wire head first, and then check the shunt switch. If the cross-section of the shunt wire is small, it should be considered that the core wire may be broken in the insulating layer and cause a local open circuit.
(3) Individual open circuits.
This type of fault is generally confined to the junction box, lamp holder, light switch, and the connecting wires between them. Usually, the connection of each joint can be checked separately, and the contact condition of the contacts of components such as lamp holders, light switches and sockets (for fluorescent lamps, the connection condition of each component should be checked).
