Terminal Block
A terminal block is a connection element that joins two or more conductors in a removable way. It produces the contact force with a screw, a spring or a push-in mechanism. Because it offers a separable point instead of a permanent joint, it makes installation, maintenance and fault diagnosis easier.
The electrical job of a terminal block is to provide a low and stable contact resistance between two conductors. Its mechanical job is to transfer the pulling force of the cable to the body rather than to the conductor.
- Screw type: contact quality depends on the tightening torque; it can loosen under vibration and thermal cycling.
- Spring and push-in type: because the spring applies a constant force it is more resistant to loosening, and assembly is fast.
- Current limit: every terminal has a rated cross-section and current; using it above that heats the body.
Terminal blocks are also the natural measuring points for fault diagnosis. When looking for a voltage drop in a circuit, measuring each side of the terminal separately lets you tell whether the problem is in the cable or in the connection. If terminal blocks are used on the supply and motor outputs of AXI drivers and remote controls, do not neglect terminating stranded ends with ferrules and re-tightening once after the first run.
Context in which this term is used: Installation, redundancy and field continuity