Several types of humid air generators are used in Europe.
Humid air generators represent a less expensive and less complicated method for calibrating dew point transfer standards and industrial hygrometers.
The different methods work in the principle of saturating air, regulating a hygrometric parameter with a very good stability and uncertainty ("two pressure method", "two temperature method").
The project investigated which one of these two methods offers superior meteorological properties.
By applying comparable tests to each of the different types of humidity generators, information was obtained about the meteorological quality of the humid air generator method (repeatability, stability, hysterisis, uncertainty). %
The project has demonstrated the equivalence of humidity measurements between the different national standard laboratories that participated in the project.
Humidity generators will now be used as a reference method for dew-point, for the industrial calibration of hygrometers.
The results have been submitted to CCT WG2, which will set uncertainties for national standard laboratories for humidity measurements.