1- Buy a fan that is driven by a motor which has exact specifications as mentioned in the datasheet 2 -Buy a PVC pipe that will fit to fan diameter, cut it in half and attach to both ends of the fan (might not fit exactly, you can fill the gaps with hot silicone gun etc) 3- Place anemometers to both ends (if only 1 available than do it by turn) 3- You can precisely control the fan speed and direction by adjusting duty cycle/period of a PWM (refer to datasheet) 4- By logging anemometer output and correlating with supplied PWM signal, you can derive the characteristic plot Let me know if it works (: On Tue, Dec 6, 2011 at 6:05 PM, Robin D. Bussell w= rote: > Hi Folks, > =A0 =A0 =A0 =A0 =A0 What are your thoughts on simple (ish ) ways of condi= tioning > the output of a fan to give a nice smooth air flow for testing an > ultrasonic anemometer? I'm not too fussed about absolute speed accuracy, > it's more having a nice smooth source to test the stability of the > direction sensing that I'm interested in. > > Something like the Dyson Air Multiplier: > =A0http://www.dyson.co.uk/store/fans.asp > =A0looks like it might make an off the shelf solution but might be > difficult to get bought (or to keep hold of once the office sees it! =A0)= .. > > Tube full of straws to induce laminar flow? =A0Just a long tube to let > things "settle down" =A0after the blades? > > Any input welcome :) > > Cheers, > > Robin Bussell. > > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .