An infrared hygrometer for atmospheric research and routine monitoring

Abstract

The development and testing of a field durable, infrared differential absorption hydrometer is described. This noncontact hygrometer offers reliable operation in harsh environments while maintaining subsecond response speed. A modified exponential response function was derived from laboratory calibration data. Absolute humidity resolution is better than 1% for absolute humidities greater than 2.0 g m-3, and better than 6% for absolute humidities in the range of 0.1-2.0 g m-3. The lower limit of sensitivity is less than or equal to 10 ppmv. A field trial was conducted at White Sands Missile Range, New Mexico, utilizing a total of six humidity sensors and four temperature sensors. The infrared hygrometer was determined to be the most accurate humidity sensor in the field trial, with a dew/frost-point measurement error of less than 0.5°C over the dew/frost-point range of -15° to 10°C. -from Author