How to check the condition of an air switch with a multimeter?
Let's take this 3 - pole air switch as an example. First, switch the air switch to the off position. Then, use the resistance range of the multimeter to measure whether the three circuits are connected. If they are not connected, the air switch is in good condition. Next, push the switch to the on position and measure the continuity. If it is connected, the air switch is good; if not, it is bad.
Due to the low accuracy of ordinary multimeters, they can only be used as auxiliary tools in daily use and cannot be used as equipment to provide specific data. Therefore, there are also certain errors when using a multimeter to check the condition of an air switch. However, for ordinary households without specialized instruments, having a multimeter to measure voltage, current, or resistance is quite useful.
An air switch has two automatic protection functions: overload protection and short - circuit protection. In addition, it can also connect and disconnect the circuit to isolate the power supply. We cannot use a multimeter to check the overload protection and short - circuit protection functions. In the laboratory, a high - current generator is used to test the overload performance. To test the short - circuit performance, a transformer, short - circuit impedance, and a data acquisition system are required. However, at home, you can use a multimeter to check whether the contact position of the air switch is consistent with the position indicated by the handle. Sometimes, after the air switch has been energized for a long time or a fault has occurred, the contacts may be welded together. In this case, even if the handle is in the off position, one or several poles of the contacts may still be in the on state. At this time, you can use the resistance range of the multimeter to check the state of the contacts.
Similarly, if there is a mechanism failure or after interrupting a large short - circuit current, the contacts may not be able to connect the circuit. When you switch the handle of the air switch to the closed position but there is no power on the load side, you can also use a multimeter to measure the voltage on the load side or measure the resistance after removing the air switch to determine whether the contacts have connected the circuit.
