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Johnson Matthey is market leader in the field of precious metal thermocouples.

Accuracy and reliability are two areas which cannot be compromised and we offer a range of thermocouple wires that conform to the strict standards that are required. All thermocouple wires supplied by Johnson Matthey are tested against international standards in our UKAS (formerly NAMAS) accredited calibration laboratory and are supplied with a Certificate of Test detailing EMF outputs.

We supply thermocouple wire ranging from the 0.03 atomic percent iron/gold v chromel for cryogenic temperature measurement, through the platinum v rhodium/platinum combinations to iridium v iridium/rhodium for measurement of temperatures above 2000° C.

Calibration standards & tolerances:

Type R, S and B thermocouple wire from Johnson Matthey is supplied in accordance with the EMF/temperature relationships detailed in IEC 584-1 (equivalent to BS EN 60584-1), based on the International Temperature Scale of 1990 (ITS-90).

Thermocouples can also be supplied based on IPTS-68 and IPTS-48 (NBS 561) if required. Thermocouple Wires are supplied in accordance with the tolerance limits set out in IEC 584-2 or to specific customer requirements.

Although not covered by the standard tolerances the 20% rhodium/platinum v 40% rhodium/platinum thermocouple is issued with a certificate guaranteeing an accuracy of +/-8°C over the whole range to EMF tables supplied. The iridium v 40% iridium/rhodium thermocouple is supplied with a calibration chart specific to individual matched batches of material, and is accurate to +/-10°C over the whole range. The 0.03 atomic percent iron/gold v chromel thermocouple should be calibrated by the user, however, reproducibility of readings will be +/-0.2% over the whole range.

Johnson Matthey has introduced a comprehensive range of options into its thermocouple wire range geared towards customer requirements. 

  •  Thermocouple wires can be calibrated as individual limbs or matched pairs using fixed point techniques or comparative methods. In addition to the above tolerances, type R & S thermocouples are available, calibrated as matched pairs to give accuracies typically of +/-1°C, over a specified temperature range or calibration point. High accuracy thermocouples are available on request e.g. +/-0.5°C at the gold point.
  • Specifications can be tailor-made to suit individual customer requirements including both calibration details and physical properties such as elongation, breaking load and UTS.
  • Thermocouples supplied as individual wires or with both thermoelements on one reel with the hot junction already formed.
  • Fine thermocouple wire for disposable cartridges available as types S, R & B in diameters down to 0.040mm or smaller if requested.

*Common sizes of S, R & B thermocouple wires are available ex-stock for immediate delivery.

*Johnson Matthey offer full technical support to our customers, including the investigation of premature thermocouple failures (determining the cause of calibration drift or breakage, evidence of any contamination during service etc).


Whether your precious metal refining requirements are large or small, as the largest precious metal refiner in the market-place today, Johnson Matthey is able to provide the refining package best suited to your needs. For more details please contact your local Johnson Matthey office detailed below.