18.03.2022

What Is A Terminal Block?

How do we connect two wires? By stripping the insulation at the ends and twisting them together? Yes, it works. But, is it safe? We can apply insulation tape over the joint or use a wire connector. But what if there are a number wires that need to be joint/connected near each other? Or, what if multiple outgoing wires are to be connected to a single incoming wire? Then this method will neither be safe nor be convenient anymore. Here we use terminal blocks.

What Is A Terminal Block?

A terminal block (also called as connection terminal or terminal connector) is a modular block with an insulated frame that secures two or more wires together. It consists of a clamping component and a conducting strip. A typical simplest terminal block is as shown in the image below.


The insulating body of a terminal block houses a current carrying element (a metal strip or terminal bar). It also provides a base for clamping element. The body has a mounting arrangement so that the block can be easily mounted on or unmounted from a PCB or a mounting rail. Most terminal blocks are usually modular and mounted on DIN rail. That allows us to increase the number of terminals according to the requirements. Terminal blocks keep connections much more secure and wires well organized.


Types Of Terminal Blocks

Electrical terminal blocks can be classified on the basis of structure, device type, termination options, etc.


Structure Type

Single level pass-through terminal blocks: These are simply used to connect two wires together, i.e. wire-to-wire connection. These are also called as single feed terminal blocks. Single level terminal blocks are of the most simple type having one input contact and one output contact.

Dual level terminal blocks: These blocks have another level of connection terminal stacked on the first one. This arrangement is generally used to save space.

Three level terminal blocks: Just like dual level blocks, these have an extra level at the top. An advantage of using multilevel blocks is that multiple connections can be made in the same block.


- Ground Terminal Block

These blocks often look like a single level feed through terminals. The exception is that these blocks and the metal connection where the wire is terminated are grounded to the panel or DIN rail on which the block is mounted.

- Fused Connection Terminals

These are similar to the pass-through blocks with an exception of the metal connection strip is replaced with a fuse. Therefore, the wires will be connected through a fuse providing an added protection.

- Thermocouple Terminal Blocks

These are designed to accept thermocouple lead connections. Some thermocouple connectors essentially clamp the thermocouple leads together on both sides of the block, eliminating the metal connection strip inside the block. However, in some thermocouple blocks, the metal connection strip of the same metal as that of the wire may be present.


There are also other kinds of Terminal Blocks like Screw Mounting Terminal Block, EK Ground Terminal Block, Push In Terminal Blocks, Terminal Fixing Block, etc. And except Terminal Blocks, other Terminal Accessories are needed for a Terminal, such as Terminal Bridge, Terminal Block End Cover, Terminal Marker Strip and Terminal Marker Carrier

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