A liquid bath for accurate temperature measurements

At the Thermometric division of the Italian Institute of Metrology (IMGC) a new liquid oil bath has been designed, manufactured and characterized with the aim to provide a suitable device for thermometers calibrations at the millikelvin level in the range from −10 °C to 100 °C. The temperature of the bath in the measuring zone is stable within a few tenths of a millikelvin in the whole range over a period of several days and it is independent from fluctuations of the ambient temperature. The bath shows a vertical and axial temperature uniformity within a few tenths of a millikelvin over 10 cm in the central part of the measuring zone. The paper describes the bath and the temperature control system. Data acquired during the characterization of the bath are reported.