Hi,
I must admit that I hadn't read that Sensiron Application Note, but it does say:
"Other devices ... like vane style ... or ultrasonic anemometers can be used to determine the speed and direction more precisely."
So it appears to be mainly intended for low cost and very small size, rather than accuracy.
An advantage of the cup anemometer and ultrasonic methods is that they have a linear response, so need only one-point calibration. In fact the "time of flight" method is the only one I know of that can be "calibrated" by design directly from basic physical properties, so potentially doesn't need to be calibrated as such. Having driven my car around with a GPS and anemometer on the roof and built an indoor "roundabout" for calibration, I can say from experience that even single point calibration is not easy.
The Netatmo Anemometer is really rather interesting, but sadly appears to be a case of "style" over practicaliity (and perhaps also wild optimism). The ultrasonic transducers appear to be facing out from a single plane, with the sound waves reflected backwards? And to have designed it without a solar panel and rechargeable batteries (which might also have helped keep the rain out) seems crazy.
Another interesting low-cost concept is the "RotoVane", a tagged cup anemometer invented by Derek Weston in the 90's. It was manufactured and sold successfully under license for ten or more years, but he has now freely released all the (PIC) Source Code for anyone who wants to "play".
Cheers, Alan.
I must admit that I hadn't read that Sensiron Application Note, but it does say:
"Other devices ... like vane style ... or ultrasonic anemometers can be used to determine the speed and direction more precisely."
So it appears to be mainly intended for low cost and very small size, rather than accuracy.
An advantage of the cup anemometer and ultrasonic methods is that they have a linear response, so need only one-point calibration. In fact the "time of flight" method is the only one I know of that can be "calibrated" by design directly from basic physical properties, so potentially doesn't need to be calibrated as such. Having driven my car around with a GPS and anemometer on the roof and built an indoor "roundabout" for calibration, I can say from experience that even single point calibration is not easy.
The Netatmo Anemometer is really rather interesting, but sadly appears to be a case of "style" over practicaliity (and perhaps also wild optimism). The ultrasonic transducers appear to be facing out from a single plane, with the sound waves reflected backwards? And to have designed it without a solar panel and rechargeable batteries (which might also have helped keep the rain out) seems crazy.
Another interesting low-cost concept is the "RotoVane", a tagged cup anemometer invented by Derek Weston in the 90's. It was manufactured and sold successfully under license for ten or more years, but he has now freely released all the (PIC) Source Code for anyone who wants to "play".
Cheers, Alan.