How to use a multimeter to check the quality of the air switch
When we use a multimeter to measure the air switch, we can only simply measure whether its continuity is good.
Let's take this 3P circuit breaker as an example. We first turn the circuit breaker to the off position, and use the resistance setting of a multimeter to measure whether the three circuits are connected. If there is no connection, it is good. Then push it to the open position and measure the continuity. If it is connected, it is good. If it is not connected, it is bad.
Due to the low accuracy of ordinary multimeters, they can only be used as auxiliary tools. It cannot be used as a device to issue specific data. Therefore, there is a certain error in using a multimeter to detect the quality of the air switch. However, ordinary households do not have special instruments. It is good to have a multimeter to measure voltage, current or resistance.
The air switch has two automatic protection functions: overload protection and short circuit protection. In addition, it can connect and break circuits to isolate the power supply. We cannot check the overload protection and short-circuit protection functions with a multimeter. We use a large current generating device to detect overload performance in the laboratory. Short-circuit performance requires the use of transformers, short-circuit impedance, and data acquisition systems to complete testing. But you can use a multimeter at home to check whether the contacts are consistent with the position indicated by the handle. Sometimes the air switch is powered on for a long time, or the contacts will be welded after a fault occurs. During the welding, even if the handle is in the open position, one or several poles of the contacts will be in the connected state. At this time, use the resistance setting of a multimeter to determine The status of the contacts can be checked.
In the same way, if the mechanism fails or a large short-circuit current is broken, the contacts may not be able to connect the circuit. When we turn the handle of the air switch to the closed position and there is no power on the load side of the switch. You can also use a multimeter to measure the load side voltage, or measure the resistance after removing it. To determine whether the contacts are connected to the circuit.
