Comparison of Sensors for Measurement of Air Humidity

Abstract

Hygrometry is a relatively old are amongst the various disciplines of physical measurement. In fact, 1983 is a memorial year, since it was just 200 years ago that the first working hair hygrometer was designed (de Saussure, 1783). The oldest hygrometer dates back to about 1500 when da Vinci described an instrument that registered changes of weight in a ball or wool. After the advent of thermometers and temperature scales, the working principles of wet bulb and dew point hygrometer were first described aroudn 1750, long before an understanding of phase changes, vapour pressure or saturation was acquired.