The Case for Chilled Mirror Hygrometry

INTRODUCTION TO HUMIDITY MEASUREMENT
Often, we wish to know several conditions of the ambient air or other gas. For example, we may need its temperature, pressure, or moisture content. For temperature, using a thermometer or solid state sensor is comparatively straight-forward. For pressure, there are many transducers that are relatively easy to configure. Where many gas measurement errors are made, however, is when humidity measurements are attempted. Quantifying the level of water molecules in a gas can be difficult and challenging. If you want to know the humidity of the ambient air in your lab, dry gas in a test chamber, a tank of bottled gas used in a manufacturing process, or outside air in a meteorological application, careful study and planning are necessary. If you need accurate and reliable results, these measurements simply cannot be taken casually. In this paper, the authors will discuss many of the commonly-used humidity sensors, and will provide information that will aid in selection of the optimum sensor for your unique measurement application.