. Thermal Sensors SENSOR FOR ULTRA LOW WIND SPEEDS AND BOUNDARY LAVER CONDUCTANCE Figure 1 above: WSOl sensor: thermopiles (1), heating wire (2), cable (3). below: graphs at different wind speeds: signal amplitude varies with 1/ wind speed or 1/C,r. WSOl is a sensor that is used to investigate the heat transfer coefficient, Ctr, from its surface to the air. The obtained data can be used to determine other transfer coefficients (for instance for water vapour transport) or local wind speed (specifically in Che low wind speed range). Both measurements are qualitative rather than absolute. WSOl is suitable for outdoor use. It has to be used combination with a proper data acquisition and control system. WSOl consists of a heater and a sensor incorporated in a very thin plastic foil. The sensor in WSOl, consisting of two thermopiles, performs a differential temperature measurement around the heating wire with record breaking sensitivity. When placing the sensor in air and switching or the heater, the sensor output will be inversely proportional to the heat transfer to the air. The main application of WSOl is as an "artificial leaf" to study mass transport in the leaf boundary layer. In this application it is a benefit that WSOl has a leaf-like geometry (flat and thin). Also WSOl can be used to study local wind speed in greenhouses and buildings. This can only be done if there is one predominant wind direction. Measurement errors induced by solar radiation are strongly reduced by the fact that the sensor sing the technique of pulsed heating. The low thermal mass makes WSOl very fast, reaching thermal equilibrium in 30 s in still air. When considering to apply WSOl it is recommended to consult the manual which is available at Hukseflux. A program for interfacing with the Campbell Scientific CR10X and CR1000 Version 0617 (page 1 of 1) Hukseflux reserve the right to alter specifications without prior notice HUKSEFLUX'" THERMAL SENSORS . WWW.HUKSEFLUX.COM , [email protected]