What Is a Terminal Block?
A terminal block is a detachable connector that connects a wire to a board/bus by clamping it with a screw or spring, without soldering.
How It Works
The stripped end of the wire is inserted into a metal slot and pressed by tightening a screw (or by a spring clamp). This makes a robust connection in the field without soldering, one that can be undone when needed.
Types
The screw terminal is the most common; the spring (push-in) terminal is vibration-resistant and fast; the pluggable terminal lets the wired part be removed entirely.
| Type | Property |
|---|---|
| Screw | Cheap, robust, hand-tightened |
| Spring | Vibration-resistant, fast |
| Pluggable | Detachable modular connection |
Where Is It Used?
Power inputs/outputs, motor and relay lines, sensor field cables, industrial control boards and power-supply connections. It's preferred on lines carrying high current.
Pitch and Current
Terminal blocks are also referred to by pitch (e.g. 3.5 / 5.08 mm), and each type has a certain current/voltage limit; the wire gauge and current must be chosen accordingly.
Ganging Side by Side
Many terminal blocks are "modular": individual blocks slide together side by side to reach the desired number of channels. In some types, bridge bars turn adjacent terminals into a common bus, distributing the same supply to several points; this simplifies assembly in distribution panels.
Common Mistakes
- Loose screw: insufficient tightening leads to heating and arcing.
- Thick wire: a wire thicker than the slot capacity shouldn't be forced.
- Stranded end: a ferrule should be used on thin stranded wires.
Frequently Asked Questions
Is a terminal block the same as a "klemens"?+
Why use a ferrule?+
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