National Physical Laboratory

Supply of high temperature eutectic fixed point cells for calibration of thermocouples (1324 °C and 1492 °C)

Thermocouple calibration

Melting point cell

NPL is able to offer for sale the novel cobalt-carbon (Co-C, 1324 °C) and palladium-carbon (Pd-C, 1492 °C) eutectic fixed points for thermocouple calibration at high temperature with ultra-low uncertainties. The high temperature fixed-point cells consist of a high purity graphite crucible containing an ingot of the eutectic alloy constructed from carbon and cobalt or palladium, each having a purity of 99.999% (99.95% purity for palladium at present, due to limited availability).

The cells are supplied with an NPL certificate showing the melting temperature of the cell determined, traceable to ITS-90, by radiation thermometry:

  • Co-C fixed-point cell (1324 °C) uncertainty: ± 0.55 °C, k = 2
  • Pd-C fixed-point cell (1492 °C) uncertainty: ± 0.73 °C, k = 2

For proper implementation, the cells require a highly isothermal environment. If desired, NPL can supply a furnace with three control zones, alumina lining tube, and graphite insulation environment. The cells are approximately 120 mm in length with a diameter of 40 mm. The re-entrant well has a diameter of 7 mm.

Furthermore, NPL is developing miniature versions of these cells, which are available to purchase for in-situ validation of thermocouple readings. These must also be operated under an inert atmosphere. See the self-validating thermocouples page for more information.

Download here details of the high-temperature fixed point (eutectic) cells available to purchase from NPL, for the calibration and validation of thermocouples.


Customer Services tel: +44 20 8943 6315

Last Updated: 27 Aug 2015
Created: 7 Sep 2009


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