Third comparison of the World Radiometric Reference and the SI radiometric scale

Ten years after the last comparison of the World Radiometric Reference (WRR) to the Système International (SI) radiometric scale and in respect of the recent introduction of a quality management system for the maintenance and dissemination of WRR, the need for a third comparison became apparent. In this third comparison, the two scales are related through two separate radiometers representing WRR and two independent realizations of SI by cryogenic radiometers at the Bundesamt für Metrologie (METAS) in Wabern, Switzerland, and at the National Physical Laboratory in Teddington, UK. The final results have confirmed the previously stated agreement between WRR and SI scales to better than 0.03% ± 0.14%.