Uncertainty of the Kriss Low Frost-Point Humidity Generator

摘要

The KRISS low frost-point humidity generator (LFPG), was developed in 2006 for the frost-point range (−95 to −40)°C in order to extend calibration capabilities. In this paper, the evaluation of the generator’s uncertainty budget is reported for which each uncertainty component was categorized and estimated by experiment and calculation. The uncertainty of the LFPG depends on the generated frost point, gas flow rate, and change of moisture concentration in transportation. The standard uncertainty of LFPG is less than 32 mK in the frost-point range from −70 °C to −40 °C. However, in the lower frost-point range, the uncertainty increases to 137 mK at −90 °C, and this is mainly due to water adsorption or desorption in the transportation tubing from saturator to hygrometer.