In modern industry, many relays are used, and different types of relays have different applications. Among relays, finder intermediate relay is used to increase the number and capacity of contacts in relay protection and automatic control systems, and also to transmit intermediate signals in control circuits. Finder intermediate relay plays an important role in industrial automatic operation system.

From the perspective of structural principle, finder intermediate relay is a kind of relay, which is composed of fixed iron core, movable iron core, spring, moving contact, static contact, coil, wiring terminal and shell. When the coil is energized, the moving iron core acts to pull in under the action of electromagnetic force, and the moving contact acts to separate the normally closed contact and close the normally open contact; When the coil is powered off, the moving iron core will bring the moving contact to reset under the action of the spring.

Due to many contacts and wide coil voltage range, finder intermediate relay is generally used to control various solenoid valves in the circuit to amplify the signal or transmit the signal to several control elements at the same time.

The basic structure and working principle of finder intermediate relay is exactly the same as that of contactor. The difference is that the number of contact groups of intermediate relay is very large. There is no difference between main contact and auxiliary contact. The allowable current of each group of contacts is the same. Because its contact capacity is relatively small, it cannot be used in the main circuit in the motor control circuit, but its small current is used to control the coil of the contactor to achieve the function of small current controlling large current.

In the industrial control circuit, it often happens that the normally closed contact of the contactor needs to be used to achieve the control purpose, but the normally closed contact of the contactor itself has been used up and the control task cannot be completed. At this time, an intermediate relay can be connected in parallel on the coil of the original contactor, and the normally closed contact of the intermediate relay can be used to control the corresponding components, change the contact type, and achieve the required control purpose.

The contact of finder intermediate relay has a certain load capacity. When the load capacity is relatively small, it can be used instead of small contactors, such as the control of electric rolling gate and some electric machines. The advantage of this is that it can not only achieve the purpose of control, but also save space and make the control part of the machine more delicate.

In some control circuits, the finder intermediate relay is often used to control the on-off of some electrical components, which is controlled by the opening and closing of its contacts, such as the automatic degaussing circuit commonly used in displays, and the triode controls the on-off of the intermediate relay, so as to control the on-off function of the degaussing coil.

In industrial control or computer control circuits, although there are various interference suppression measures, the interference phenomenon still exists more or less to remove the interference in the circuit.