Thermocouple Products

Thermocouple

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Thermocouple

A thermocouple is a temperature sensor made from two conductors of dissimilar metals joined at one end, which generates a small voltage proportional to the temperature difference between the measuring junction and the reference junction.
Thermocouple Products manufactures thermocouples in types J, K, T, E, R, S and B at its facility in Edenvale, Gauteng, in single and duplex configurations for temperatures from −250°C to +1 600°C.

How It Works

  • Thermoelectric Effect: When two dissimilar metal conductors are joined and the junction is heated, an electromotive force (EMF) is generated. This voltage is measured in millivolts and is proportional to the temperature difference between the hot junction and the reference junction.
  • Measuring Junction: The welded joint at the sensing tip. Thermocouple Products forms this junction by argon arc micro-welding, a technique the company pioneered in South African thermocouple manufacture, which produces a clean, mechanically sound junction that resists contamination and drift.
  • Reference Junction: The point where the thermocouple connects to the measuring instrument. Because the sensor measures a difference, the instrument must know this reference temperature — modern instruments determine it electronically through cold junction compensation.
  • Extension Cable: Matching thermocouple extension or compensating cable carries the signal to the instrument. Ordinary copper wire cannot be used, as it creates additional thermoelectric junctions and introduces measurement error.

Key Specifications & Features

  • Operating Temperature: −270°C to +1 600°C across the full range, depending on calibration type and sheath material.
  • Calibration Types: J, K, T, E, R, S and B, available single or duplex.
  • Sheath Diameters: From 1,5 mm in mineral insulated construction to 32 mm in heavy carbon steel protection sheaths.
  • ImmersioInsertion Lengths: 100 mm to 2 000 mm as standard, with longer lengths manufactured on request.n Heating: Liquids or gases when fitted with threaded fittings or protective flanges.
  • Accuracy: Standard limits of error to recognised ISA tolerances, with special limits of error available on request — typically halving the permissible error.
  • Response Time: Fast, particularly in small-diameter mineral insulated construction with a grounded junction.
  • Customisation: Any length, sheath material, diameter, junction type, termination and process connection manufactured to order. Sensors can also be built to a customer's drawing or sample.

Common Applications

  • Plastics Processing: Barrel, nozzle and hot runner measurement on injection moulding and extrusion machinery, where fast response and vibration resistance determine product quality.
  • Furnaces, Kilns & Heat Treatment: Foundries, forges and heat treatment plant, using noble metal elements with ceramic protection at the upper end of the range.
  • Petrochemical & Chemical Processing: Reactors, columns and pipelines, where sheath material must be matched to the process medium and the sensor is normally installed inside a thermowell.
  • Power Generation: Boilers, superheaters, turbines and flue gas measurement under high pressure and sustained thermal cycling.
  • Steel & Metals: Molten metal, ladle and furnace measurement, where types R, S and B operate above the range of any base metal sensor.
  • Food, Beverage & Pharmaceutical: Ovens, sterilisers and autoclaves, where a hygienic stainless steel sheath and rapid response are required.

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