How to use a multimeter to check the quality of the air switch
Taking this 3P circuit breaker as an example, we first turn the circuit breaker to the open position and use a multimeter to measure whether the three circuits are connected. If they are not connected, it is good. Then push it to the open position, measure the continuity, whether it is good or not, and whether it is bad or not.
Due to the low accuracy of ordinary multimeters, they can only be used as auxiliary tools in daily life. It cannot be used as a device to provide specific data. So using a multimeter to check the quality of the air switch also has a certain degree of error. However, ordinary households do not have dedicated instruments, and having a multimeter to measure voltage, current, or resistance is also very good.
The air switch has two automatic protection functions: overload protection and short circuit protection. In addition, it can also connect and disconnect circuits to isolate the power supply. We cannot check the overload protection and short circuit protection functions with a multimeter. To test the overload performance in the laboratory, a high current generating device is used. The short-circuit performance requires the use of transformers, short-circuit impedance, and data acquisition systems to complete the testing. But at home, you can use a multimeter to check if its contacts are consistent with the indicated position on the handle. Sometimes, when the air switch is powered on for a long time or malfunctions, the contacts will melt. Even if the handle is in the open position, one or several poles of the contacts will still be in the connected state. At this time, the resistance range of the multimeter can be used to check the status of the contacts.
Similarly, if the mechanism malfunctions or breaks a large short-circuit current, the contacts may not be able to connect to 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 voltage on the load side, or remove it and measure the resistance. To determine whether the contact is connected to the circuit.
