Interlaboratory Comparison of Reference Surface Temperature Apparatus at NMIs

During 2001 and 2002, the first international comparison of surface temperature measurements at national metrology institutes (NMIs) was organized under EUROMET Project No 635. The coordinator for this project was the National Office of Measures (OMH) in Hungary. Among the participants were the Swedish National Testing and Research Institute (SP) from Sweden, the Centre for Metrology and Accreditation (MIKES) in Finland, and Justervesenet (JV) in Norway. The comparison showed a need for better apparatus to reduce the differences in the results from the different laboratories. As a result, a new apparatus was designed at SP and MIKES made some changes to their apparatus. To test the new and modified apparatus, SP took the initiative to arrange and coordinate a new comparison. In this recent comparison, measurements were made at temperatures from 50 to 300°C on surfaces of aluminum and stainless steel. The comparison was arranged and performed during 2005 and 2006. Participants in the comparison were OMH, MIKES, RISOE, JV, and SP. The comparison results using the newly developed apparatus show improved agreement with the earlier EUROMET intercomparison, but also indicate a need for a more standardized calibration method and apparatus to be able to perform calibrations in different laboratories with good agreement.