Method for measuring the moisture content of air
J. J. Higgins · Journal of Scientific Instruments · 1959
The water vapour in a sample of air is first condensed as ice and subsequently allowed to evaporate at room temperature, so causing a pressure rise in a closed, evacuated system, the pressure being measured by a simple oil manometer. The apparatus for doing this is described in detail and, by a calibration of the instrument with known masses of water vapour, a factor can be obtained that converts the observed vapour pressure to absolute humidity with an overall accuracy better than 1%. The apparatus has also been used to study the relationship between water vapour pressure e (mm of mercury) and absolute humidity h v (g/m 3 ). A value of 286.4 ± 1.7 was obtained for the constant C in the equation h v = Ce/T where T was the absolute temperature (° K).