How to judge the quality of various relays?

When the rated voltage is applied, the solenoid can be normally closed and can be reset normally after the power is cut off. When the coil is not energized, the normally closed connection should be correctly connected, and the normally open connection should be maintained alternately. After the coil is energized, the normally open connection should be correctly connected, and the normally closed connection should be connected in series. This relay is very good.

Use the electric barrier of a multimeter to measure the resistance of normally closed connections and moving points. The resistance value should be 0; the scale resistance and the moving point of the normally open connection are not restricted. , This is the normally open coordinate. Use the R×1 block of the multimeter to measure the resistance value of the normally closed contact, which is usually 0; otherwise, it is 0. Press the armature, the resistance of the normally closed contact should be infinite at this time. If the armature is not pressed, the normally closed group will be measured as having a certain resistance or infinity, which means that the connection of the group has been burned or oxidized.

The resistance of the electromagnetic relay coil is generally 25Ω~2kΩ. If the measured resistance is less than infinity, it indicates that the coil is damaged or damaged; otherwise, it indicates that it is damaged. If the measured resistance is much lower than the normal value, it indicates that there is a short-circuit fault inside the coil. If the coil is partially short-circuited, it is not easy to find using this method.