Journal Archive

Platinum Metals Rev., 1973, 17, (2), 56

Connectors for Metal Clad Thermocouples

Plug-in End Caps for Compensating Leads

A new type of end connector recently developed by Johnson Matthey Metals Limited enables the compensating lead to be disconnected from the thermocouple, so making thermocouple replacement simpler. The new unit makes it possible to connect one lead in turn to any number of thermocouples, thus saving on the number of leads and temperature recording instruments.

Housed within the anodised aluminium case are gold plated pins and sockets, to which are soldered the thermocouple wires and the compensating cable respectively. The assembly is then encapsulated in nylon to form a two-piece connector, each half bearing corresponding flats to ensure correct polarity with every connection.

These end connectors satisfactorily withstand operating temperatures of up to 100°C, the normal working temperature of the compensating lead. At this temperature stray e.m.f.s at the pin and socket junctions are negligible and do not affect output of the thermocouple.

Colour coding of the aluminium cases easily identifies thermocouples; red denotes platinum: 13 percent rhodium-platinum, gold denotes platinum: 10 per cent rhodium-platinum, and silver or neutral colour other combinations (5 per cent Rh-Pt:20 per cent Rh-Pt, 6 per cent Rh-Pt:30per cent Rh-Pt, Pallador).

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