Abstract
Two-dimensional humidity distribution can be measured based on the infrared absorption principle, when an infrared beam is introduced into the humidity field from its one side through an optical fiber and the damped beam is caught from the other side of the field by another optical fiber. This paper proposes a measuring system and presents its calibration results.
Moist air of known dew-point as 20, 25, 30, 35 and 40°C of 16cm and 30cm optical path length and infrared light of 1.86μm wave length are used in the calibration test. Apparent absorption coefficents obtained based on Beer's law are 0.043 (kPa·m)-1 and 0.034 (kPa·m)-1 and the accuracy of the present measurement is estimated to be ±3g/m3 and ±2g/m3 for 16cm and 30cm optical path, respectively. These results suggest the necessity of case by case calibration at present. Some proposals for improving the elements of the measuring system are also discussed, particularly for measuring low humidity.
