DESIGN CRITERIA FOR A SENSITIVE INFRARED-ABSORPTION HYGROMETER

摘要

This report presents design criteria for a device to measure atmospheric eater-vapor content by using absorption techniques in the infrared region. In discussing the absorption theory and basic relationship, the report shows that the well-known square root relationship is valid for some of the absorption range only; below a certain level the response is linear. It is pointed out that the absorption function in the linear range should be independent of pressure. The report also describes a laboratory model of the hygrometer. Although this device is still in the experimental stage, the ultimate objective is to make the design sensitive and .accurate enough for use at the low tempera¬tures and low pressures encountered by aircraft.