Many alternative types of terminal head are available to meet the requirements of various applications. Variations exist in size, material, accommodation, resistance to media, resistance to fire or even explosion and in other parameters. Common types are shown below but there are many special variants available to meet particular requirements.
DIN standard 43 729 defines two such types of head which dominate the European market. Identified as Types A and B. The smaller Type B version, is the most popular and 2 wire transmitters are usually designed to fit inside the DIN B head. Terminal block located in a “head” allow for the connection of extension wires. Various materials are used for screw or solder terminations including copper, plated brass and, for the best performance in the case of thermocouples, thermoelement alloys. The various head styles cater for a wide variety of probe diameters and cable entries.
Alternatives to terminal heads include extension leads directly exiting probes, plug and socket connections fitted to probes and “tails” (short connecting wires). Cost savings can be thus realised when a head is not required although overall ruggedness may be limited to some extent especially when a direct extension lead is specified. Robust cable types are available.