How to Test a Four Terminal Relay

A 4 terminal relay is used so a low power circuit may engage a high power circuit without risk of damage to the low power control circuit. For example, a low power circuit in a car that commands the high power headlights to come on would send the command through a 4 terminal relay. Use these tips to learn how to test a 4 terminal relay.

EditSteps

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   Find and remove the relay. The relay should not be tested while it is connected to the circuit. The relay is typically located in a place where larger electric parts are placed. In a car, this is likely a relay or fuse box. Use your fingers to unplug the relay from the socket in which it is placed.
   • Note the relay position. The positioning and polarity of relays and fuses should be printed on the inside of the relay box or fuse box cover. Note the position of the relay that was removed so that it may be replaced in the proper position and orientation.

Working of Relays

What is a relay?

We know that most of the high end industrial application devices have relays for their effective working. Relays are simple switches which are operated both electrically and mechanically. Relays consist of a n electromagnet and also a set of contacts. The switching mechanism is carried out with the help of the electromagnet. There are also other operating principles for its working. But they differ according to their applications. Most of the devices have the application of relays.

Why is a relay used?

The main operation of a relay comes in places where only a low-power signal can be used to control a circuit. It is also used in places where only one signal can be used to control a lot of circuits. The application of relays started during the invention of telephones. They played an important role in switching calls in telephone exchanges. They were also used in long distance telegraphy. They were used to switch the signal coming from one source to another destination. After the invention of computers they were also used to perform Boolean and other logical operations. The high end applications of relays require high power to be driven by electric motors and so on. Such relays are called contactors.

TAKE A LOOK : TYPES OF RELAYS

TAKE A LOOK : HOW TO TEST A RELAY

Relay Design

There are only four main parts in a relay. They are

• Electromagnet
• Movable Armature
• Switch point contacts
• Spring

The figures given below show the actual design of a simple relay.

Relay Construction

It is an electro-magnetic relay with a wire coil, surrounded by an iron core. A path of very low reluctance for the magnetic flux is provided for the movable armature and also the switch point contacts.  The movable armature is connected to the yoke which is mechanically connected to the switch point contacts. These parts are safely held with the help of a spring. The spring is used so as to produce an air gap in the circuit when the relay becomes de-energized.

How relay works?

The working of a relay can be better understood by explaining the following diagram given below.

Relay Design