Seminar

Las mañanas IFCA con Graham Machin: "Progress in realising the redefined kelvin"

​"In May 2019 the SI underwent what was its biggest change since its introduction when the definition of four of the seven SI base units were changed to be based on defined values of fundamental physical constants. Since the change, the kelvin is now defined in terms of the Boltzmann constant, the ampere on the electron charge, the kilogram on the Planck constant and the mole on the Avogadro constant. The redefinition of the kelvin has opened several new possibilities for traceable thermometry direct to the kelvin definition. These could include using primary thermometry to directly calibrate sensors at National Measurement Institutes (NMIs) and in the medium term in calibration laboratories dispensing with traceability by the defined scales (ITS-90, PLTS-2000) and so disseminating thermodynamic temperature. In the longer term these changes could lead to the rise in potential, paradigm changing, approaches to temperature sensing such as traceability at the point of measurement both through self-validating thermometers and more radically by the deployment of practical primary thermometry based on fundamental physics and where temperature sensor itself will, unlike today, no longer need calibrating to provide traceability. In this talk an introduction to the kelvin redefinition and to the mise en pratique for the definition of the kelvin (MeP-K) will be given. How traceable temperatures are attained will be discussed, both presently, through the defined scales and how, in the medium and long term, this is likely to shift; with thermodynamic temperature approaches becoming increasingly prevalent. The talk will end by introducing novel approaches to temperature traceability including provision of NMI like uncertainty thermodynamic temperatures in calibration laboratories and the rise of in-situ/in-process traceability and the implications, particularly in the context of digitalisation and the need for “points-of-truth” in for example autonomous sensor networks".