I have one very similar to this (not with me now so I dont know the make/model - but I had a great deal of trouble trying to calibrate a drag type 3 cup [AAG] anemometer by using the hand held anomometer. I had one person on a long ladder holding the little anemometer at the same height and shouting the figures they were reading on the lcd to another person looking at a notebook screen seeing RPM figures spooling up coming from the cup anemometer. I tried to roughly plot a graph of the viewed wind speed & the RPMs to get the RPM to wind speed ratio but it was madly out and I still (a year or more later?) dont have the AAG anemometer correctly calibrated. I'm sure that both units can read the wind speed fine but that vertical axis [drag?] cup anemometers and horizontal axis [lift?] anemometers much react to gusts differently. Maybe the uni-directional aspect of the hand held units effects readings too.
Derek