Optical hygrometer using differential absorption of hydrogen Lyman-α radiation
Abstract
An optical hygrometer based on the differential absorption of the H Lyman-alpha line has been designed and built for use in atmospheric field studies. The absorption is determined along two separate paths containing sample and dry reference air, respectively, hence eliminating undesired absorption by O2. At the same time the differential absorption eliminates problems related to intensity variations in the light source output. The dynamic range of the instrument can be tuned by diluting the sample with reference air. Frequent adjustment of the zero offset allows detection of water vapor concentrations of about 3.1 x 10 to the 14th molecules/cu cm (0.01 g/cu cm). With a water vapor concentration of 3.1 x 10 to the 15th/cu cm (0.1 g/cu cm) the relative error is 10 percent. At those concentrations normally encountered in the troposphere the measuring accuracy is 3 percent. The response time of the present instrument is less than 1 s.
- Publication:
-
Applied Optics
- Pub Date:
- August 1987
- DOI:
- 10.1364/AO.26.003083
- Bibcode:
- 1987ApOpt..26.3083Z
- Keywords:
-
- Absorptivity;
- Hydrogen;
- Hygrometers;
- Lyman Alpha Radiation;
- Optical Equipment;
- Calibrating;
- Optical Thickness;
- Performance Tests;
- Water Vapor;
- Instrumentation and Photography;
- HYDROGEN;
- CLOUDS;
- ABSORPTION;
- WATER;
- GASES;
- ULTRAVIOLET: VACUUM;
- ATMOSPHERES;
- METEOROLOGY