抄録
Two types of systems for measuring local humidity with optical fibers using infrared absorptimetry of water-vapor are proposed and the calibration results are presented. One uses a PbS infrared detector and a beam through 1.86μm narrow band pass filter (NBPF) and another uses a Ge detector and a beam through 1.37μm NBPF. Moist air with known dew-points of 10°C, 15°C, 20°C. 25°C and 30°C, and with 11 cm, 17 cm, 23 cm and 31 cm optical paths, respectively are used in the calibration test. Apparent absorption coefficients obtained, based on Beer's law, are 0.042 (kPa·m) -1 (the former system) and 0.035 (kPa·m)-1 (the latter system), for different path lengths and the accuracy of the present measurements are estimated to be±1.1 g/m3 (the former system) and ±0.7 g/m3 (the latter system) for a 31 cm optical path. These results show that the latter system is more accurate at the present state and that the NBPF system is nearing a practical application.
