Felix - Model FT3010 Series - Electrically Aspirated Thermometer
Electrically Aspirated Psychrometer FT3010 series provide continuous measurements of the 'dry bulb' and 'wet bulb' temperatures with high accuracy. From these two values the desired relative humidity and dew point temperature may be obtained by using psychrometric tables, diagrams or a computer system. The design of the instrument essentially eliminates the effects of wind and radiation. Inside the downward inclined radiation shield tubes, two platinum resistance thermometers (Pt100W) are mounted. One sensor is continuously moistened with water through a wick, hereby measuring the wet bulb temperature.
The wet bulb sensor can be recognized by a groove in the base of the radiation shield. The sensors use either a 3-wire or 4-wire supply system. In this way, measurement over long distance can be carried out without the line resistance effect on the measurement. The resistance thermometers are continuously aspirated by a ventilating system providing an air flow of about 3.5 m/s. The direction of the air flow opposes the direction of water supply to the wet bulb sensor (counter flow process) to avoid pre-evaporation.