Proposes a method to determine the indirect measurement uncertainties of the humidity mixing ratio of moist air. To ascertain the validity of the method, the theoretical results were verified by comparing experimental results obtained from a number of commercially available thermo-hygrometers. The comparisons were made as relative humidity and temperature varied. A further investigation was undertaken on the long-term behaviour of thermo-hygrometers. The results indicate the validity of the proposed theoretical model.

KEYWORDS: measuring, humidity, moisture, comparing, experiment, hygrometers, relative humidity, temperature, behaviour, calculating