A Relative Humidity Calibration from 5 Degrees C to 45 Degrees C in a Mixed-Flow Humidity Generator

The paper presents a method used in the Vinca Institute of Nuclear Sciences for a reliable and traceable relative humidity calibration in the temperature range from 5 degrees C to 45 degrees C. Inside a controllable temperature and humidity environment, supplied by a mixed-flow humidity generator, measurements of hygrometers under calibration are compared with those of calibrated reference instruments. A traceability chain from temperature to reference relative humidity and next to the hygrometers under calibrations is provided by using a chilled-mirror dew-point temperature system and precise relative humidity probes. Corresponding calibration uncertainties are analyzed, particularly those associated to the temperature uniformity of controlled calibration environment. Two examples of relative humidity calibration with dew-point and relative humidity reference measurements in the range from 15 to 75% of RH and 5 degrees C to 45 degrees C are presented and discussed.