A PRELIMINARY INVESTIGATION OF CETIAT NEW HUMIDITY GENERATOR FOR AIR DEW/FROST-POINT TEMPERATURE IN THE RANGE FROM -80°C TO 15°C

摘要

For dew-point temperatures ranging from 0°C to +80°C, a comparison between humid air generators showed that they're so closely comparable that they can directly provide dew-point temperature, without reference to the gravimetric method [1]. Nevertheless, in the range from -80°C to 0°C, the outcome was less conclusive, and work had still to be done. A new humid air generator has been designed by CETIAT (France), for the range from -80°C to +15°C, to be as close as possible to the definition of dew-point temperature. The generator's chamber is equipped with specific temperature probes which enhance the influence of the different parameters acting on the uncertainties. Furthermore, the uncertainties on the reference temperature measurement are reduced by using a 25 ohms probe respecting the criteria of the ITS-90, calibrated to the fixed-points of temperature scale. The experimental results show that we can estimate the influence of the airflow on the equilibrium in the generator's chamber. In addition to the other sources of uncertainties, this knowledge will gives us new means to estimate the global uncertainties of the generator, leading us to a new step in the establishment of the primary reference in dew-point temperature.