Multimeter Testing for Open-Circuit Faults in Lighting Circuits
When the lighting circuit is open, there is no voltage in the circuit, the lighting does not light up, and the electrical appliances cannot work. The reasons include: blown fuses, broken wires, loose wire ends, damaged switches, etc.
When detecting an open circuit fault in the lighting circuit with a multimeter, the resistance range of the multimeter can be used to measure the continuity of the circuit when the power is disconnected; It is also possible to use a multimeter to measure the voltage of the circuit in the AC voltage range while power is on to determine the fault point.
Lighting circuit open circuit faults can be divided into three situations: complete open circuit, partial open circuit, and individual open circuit.
(1) All open circuits
This type of malfunction mainly occurs on the main line, in distribution and metering devices, and within the range of incoming devices. Usually, the first step is to check the connection points of each joint in the above section (including the melt connection pile) in sequence, and the common fault is the disconnection of the wire end from the connection point; Secondly, check the opening and closing status of the dynamic and static contacts of each circuit 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 branch switch. If the cross-sectional area of the branch wire is small, it should be considered that the core wire may break inside the insulation layer and cause a local open circuit.
(3) Individual open circuit
This type of fault is generally limited to the range of junction boxes, lamp holders, light switches, and the connecting wires between them. Usually, the connection of each joint, as well as the contact status of components such as lamp sockets, light switches, and sockets, can be checked separately (for fluorescent lamps, the connection status of each component should be checked).
