How to use a multimeter to check the quality of an air switch
We can only use a multimeter to measure the air switch simply to see if its on/off is good.
Taking the 3P air switch as an example, we first set the air switch to the open circuit position and measure whether the three circuits are connected using the resistance range of a multimeter. If not, it is good. Then push it to the open position and measure whether it is on or off, whether it is good 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 there is also a certain degree of error in using a multimeter to check the quality of the air switch. However, ordinary households do not have specialized instruments. They have a multimeter to measure voltage, current, or resistance, which 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 the circuit, playing a role in isolating the power supply. The overload protection and short circuit protection functions cannot be checked with a multimeter, and a high current generator is used to test the overload performance in the laboratory. The short-circuit performance requires the use of transformers, short-circuit impedance, and data acquisition systems to complete the detection. But at home, you can use a multimeter to check if the contacts match the position indicated by the handle. Sometimes, when the air switch is powered on for a long time, or when a malfunction occurs, the contact will melt. Even if the handle is in the open position, one or several poles of the contact will still be connected during the melting process. At this time, the resistance level of the multimeter can be used to check the status of the contact.
Similarly, if the mechanism malfunctions or a large short-circuit current is cut off, 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 voltage on the load side, or measure the resistance after removal. To determine if the contact is connected to the circuit.
