Bilateral comparison of humidity standards between UME and MIKES

In order to assure the quality of dew-point measurements, a bilateral comparison between the National Metrology Institute of Turkey (UME) and the Centre for Metrology and Accreditation (MIKES), Finland, was carried out in 2006. This comparison is registered as EUROMET Project No. 906. Two chilled-mirror hygrometers (MBW 373 and MBW 373H) were used to compare the UME two-pressure humidity generator with the MIKES dew/frost-point generator. An MBW 373 was used in the range from a frost point of −20 °C to a dew point of +20 °C and an MBW 373H in the range from a frost point of −20 °C to a dew point of +60 °C. Dew-point temperature measurements were performed at six dew-point temperatures in the range from a frost point of −20 °C to a dew point of +60 °C at UME and MIKES. According to the results, the mean difference between the laboratories varies from (−0.11 to +0.07) °C over the range. The estimated expanded uncertainty (k = 2) varies from (0.13 to 0.28) °C. A detailed description of the equipment, results and uncertainty analysis is presented in this paper.