Intercomparison of the dew-point temperature realizations at LPM and MIKES in the range from -70°C to +20°C

The first European humidity key comparison EURAMET-T.K6 was completed in 2008, and it covered the dew-point temperature range from -50°C to +20°C. Both LPM and MIKES participated in the comparison, but a new low dew-point generator was introduced at LPM as a result of progress in the EUROMET P912 project. To extend the range of available comparison evidence down to -70°C and to study the validity of improved uncertainties of LPM, a bilateral comparison was carried out between LPM and MIKES in 2009-2010. The applied comparison procedure was similar to that applied in EURAMET-T.K6. However, only one transfer standard was used instead of two units and the measurement point -70°C was added in the measurement scheme. The results show that the bilateral equivalence between LPM and MIKES is between (0.00 ± 0.06)°C and (0.02 ± 0.08)°C in the range from -50°C to + 20°C and (0.01 ± 0.10)°C at -70°C. Using MIKES results as the link to the EURAMET.T-K6, it is shown that the difference between the results obtained with the new LPM dew-point temperature standard and the EURAMET Comparison Reference Values is between (-0.02 ± 0.08)°C at 20°C and (+ 0.02 ± 0.07)° C at -50°C.