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Looking for a way to calibrate an anemometer in order to measure the wind speed

gekkoscamp

Hello guys,

(My first post on this forum, so ill introduce myself post scriptum)

To get into smart home systems and arduino, I am currently building a weather station measuring temperature, humidity and all kinds of funny stuff.

I am ALSO measuring the rotations of a self built 3d printed anemometer. I know the dimensions of the "flaps/cups", i know the rotations/frequency with which the thing is spinning

but i simply cant think of how to calculate the windspeed, given rotations and the drag value of a half sphere (in German its called Cw-Wert).

The actual spinning part consists of 3 equally spaced "arms" of length d each with a half sphere with diameter a.

 

How do I calculate the Windspeed, given those parameters?

 

Any hints are super appreciated.

 

----

Hi, this seems like a really cool and friendly forum so i decided to sign up.

My Name is Michael, studying engineering in Germany, eager to learn the basics of electronics and programming.

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  • hey guys, thanks for the great input.
    As some mentioned friction, very correctly, doesnt behave linearly which would overcomplicate a very accrate complication.

    And i lack of the tools to measure at the moment.

    But i love the idea of calibrating it by giving it a rough reference speed by car or another vehicle and do it this way.

    My uni does have a windtunnel tho, so i am thinking of continuing with the rest of the project until i have the opportunity to test it there... or a car if that doesnt work.

     

    @christina, as John pointed out. I enjoy it building it myself.

     

    Thanks again for all the hints.

     

    Stay healthy and have great holidays!

  • in reply to gekkoscamp

    Hi gekkoscamp,

     

    I was curious how you are measuring the fan rotations. Are you using a counter or is it a dynamo?

     

    John

  • in reply to jw0752

    I am using hall efect sensors.

    The rotating part has two light weight permanent magnets embedded in its housing while i mounted a hallsensor on the stationary axis.

    every second time a magnet passes the hallsensor i measure the time delta between the previous time-measurement and the new one and from there I form the frequency.

     

    this is implemented as a interupt service routine at the moment but i am thinking of overhauling the hole concept.

    Cant find the time to reinvent that before i havent figured out my calibration problem.

     

    Hope i could help.

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  • in reply to jw0752

    I am using hall efect sensors.

    The rotating part has two light weight permanent magnets embedded in its housing while i mounted a hallsensor on the stationary axis.

    every second time a magnet passes the hallsensor i measure the time delta between the previous time-measurement and the new one and from there I form the frequency.

     

    this is implemented as a interupt service routine at the moment but i am thinking of overhauling the hole concept.

    Cant find the time to reinvent that before i havent figured out my calibration problem.

     

    Hope i could help.

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