Fixed Point Calibrations

What is a fixed point in temperature calibration?

A fixed point is a reproducible physical event that has a defined temperature value assigned on the ITS90. An example of a conventional fixed point used in temperature calibrations is the freezing point of a pure metal such as Tin.
Tin, for example, freezes (goes through the transition from a solid to a liquid) at 231.928 °C

Our extensive list of thermal calibration fixed points allows CCPI Europe to calibrate thermocouples and platinum resistance thermometers over the operational range required by customers.

How do you calibrate a reference standard thermocouple?

The emf output of a thermocouple is measured when tested during a fixed-point transition and therefore the absolute value and difference from standard output tables can be established for that temperature point. A reference thermocouple calibration is conducted by measuring the output of the thermocouple at a number of these fixed points and from the test results, developing an individual emf output curve for the thermocouple.

Fixed Points used in the CCPI Europe Calibration Laboratory;

  • Triple point of Water 0.01 °C
  • Tin (Sn) 231.928 °C
  • Zinc (Zn) 419.527 °C
  • Aluminium (Al) 660.323 °C
  • Silver (Ag) 961.78 °C
  • Gold (Au) 1064.18 °C
  • Cobalt Carbon (CoC) 1324.02 °C
  • Palladium Carbon (PdC) 1491.16 °C
  • Palladium (Pd) in air 1553.5 °C

The CoC and PdC fixed points unlike most eutectic conventional pure metal fixed points are examples of a new range of metal carbide fixed points developed by the NPL (National Physical Laboratory) to help increase accuracies in the high temperature range above 1100 °C.