ESTIMATION OF INITIAL AND RESPONSE-TIMES OF LASER DEW-POINT HYGROMETER BY MEASUREMENT SIMULATION

The initial and the response times of the laser dewv-point hygrometer were evaluated by measurement simulation. The simulation was based on loop computations of the surface temperature of a plate with dew depos ition, the quantity of dew deposited and the intensity of scattered li ght from the surface at each short interval of measurement. The initia l time was defined as the time necessary for the hygrometer to reach a temperature within +/-0.5 degrees C of the measured dei point from th e start time of measurement, and the response time was also defined fo r stepwise dew-point changes of +5 degrees C and -5 degrees C. The sim ulation results are in approximate agreement with the recorded tempera ture and intensity of scattered light of the hygrometer. The evaluated initial time ranged from 0.3 min to 5 min in the temperature range fr om 0 degrees C to 60 degrees C, and the response time was also evaluat ed to be from 0.2 min to 3 min.