Please note this course is only available for private cohorts. Please contact NPL Training if you would like more information on enrolling a cohort.

The kelvin is the SI unit of thermodynamic temperature, and one of the seven SI base units. Unusually in the SI, we also define another unit of temperature, called the degree Celsius (°C). Temperature in degrees Celsius is obtained by subtracting 273.15 from the numerical value of the temperature expressed in kelvin.

Prior to May 2019, all temperatures were defined relative to the triple point of water, the temperature at which water can exist as a solid (ice), a liquid and a gas (water vapour). The temperature at which this condition occurs was defined to be 273.16 K exactly, and every temperature measurement was fundamentally a measure of how much hotter or colder something was than this standard temperature. Whilst convenient for ambient temperatures, this definition increased the uncertainty of measurements at very high and very low temperatures.

Since May 2019, the kelvin and degree Celsius have been defined by taking a fixed numerical value of the Boltzmann constant, k or kB. This change in definition acknowledges that temperature is fundamentally a measure of the average energy of molecular motion.

The Kelvin and Thermal Metrology course is part of National Physical Laboratory’s (NPL) Fundamentals of Metrology training programme. The programme is comprised of seven standalone modules, each corresponding to one of the seven SI base units. The module is delivered via a series of pre-recorded video lectures and includes a scheduled live group Q&A session with metrology experts from NPL. Please note this course is only available for private cohorts. Please contact NPL Training if you would like more information on enrolling a cohort.

This course includes the following topics:

• The definition of the kelvin and primary thermometry approaches.
• Temperature scales: past, present and future.
• Basics of practical traceable thermometry.
• Introduction to thermocouples and their use.
• Principles of practice and pitfalls of non-contact thermometry.

Learners who successfully complete the course will receive an NPL Certificate of Completion.

Module Prerequisites
To lay the foundations for this module, all learners are provided with access to two half-day NPL e-learning courses: Introduction to Measurement and Metrology and Introduction to Measurement Uncertainty. Learners should complete both of these courses before starting this module.