# Wind Speed Measurements

Discussion in 'The Projects Forum' started by Dammi, Feb 15, 2011.

1. ### Dammi Thread Starter New Member

Feb 15, 2011
16
0
Hi there guys, awesome site you got here

I've got some homework assignment, and I was wondering what would be the best setup to measure windspeed accuratly.

What method is the best one? Using a brushless DC motor and measuring the voltage it generates or a magnet switch on the blade and measure how often it pulses ?

Or any other method?

Best regards,
Dammi

2. ### someonesdad Senior Member

Jul 7, 2009
1,585
141
There are lots of different methods out there -- I suggest you consult your local technical library. Also do some research about the commercial instruments available and what techniques they use. Look up the word anemometer.

3. ### wayneh Expert

Sep 9, 2010
12,361
3,220
+1

If you need to build one, the bicycle speedometer approach is probably the easiest. Moving magnet makes a pulse, computer counts pulses and converts to various outputs. Temperature differential is another method that's not too hard but I think it's better at higher speeds (jet airplanes, for instance).

The problem with ALL methods is linearity. You need the speed of rotation to be directly proportional to wind speed. That means good bearings and blade design.

4. ### Dammi Thread Starter New Member

Feb 15, 2011
16
0
Alrighty, thanks for the reply guys

5. ### ahto555 Member

Mar 12, 2009
11
0
Have you been thinking about ultrasonic measuring. No moving parts. There are few quite good circuits available in internet.

Apr 5, 2008
15,796
2,382
7. ### Dammi Thread Starter New Member

Feb 15, 2011
16
0
It has to be operational outside, so one would think that rain/snow would be to much of a factor in that case

I think a regular Cup anemometer would be the best choice in my case. After some reading I really "fell in love" with Hot-Wire Anemometer, but again, the rain would propably be a factor. And correct me if I'm wrong, but wouldn't the temperature of the air also affect the measurements, so I would have to take that also into account in the reading Too much work I think for this project.

But thanks for all the replys, I'll post a picture of the project when it's finished

8. ### floomdoggle Senior Member

Sep 1, 2008
217
2
Air temp shouldn't make any difference. Also, look up the Easter egg anemometer. Ans check out the Chispito wind generator.

9. ### wayneh Expert

Sep 9, 2010
12,361
3,220
No, the heated probe approach I mentioned is designed to compensate for ambient, usually by having one probe in the wind and another not exposed. They can also designed to be immune to rain and such.

But I still recommend a mechanical approach, a spinning magnet.

10. ### Dammi Thread Starter New Member

Feb 15, 2011
16
0
Ahh yes, I found that out (about the thermal anemo meter).

But one question about using a magnet to measure the speed, won't there be alot of disturbance when the wind is very slow ?
(In other words, won't the magnet create noize in the signal when it goes really slowly towards/and over the sensor)

Wouldn't using a light gate be better ? (I get extra points for accuracy)

11. ### wayneh Expert

Sep 9, 2010
12,361
3,220
Light gate is fine, and probably even easier for a DIY project, since you can buy pre-made "gap" modules. An old VCR I recently took apart had some in it.

You may still have a noise issue, though. You'll want to modulate the beam and reject anything not coming into the receiver on the beam. That'll reject ambient noise. And you may need to have some sort of timer circuit to lock out switching for a brief period after one pulse has been detected, so that a slow pass doesn't turn into multiple triggers. The challenge will be to prevent multiple pulses while still allowing the meter to read to high rpm. I think it might work fine all by itself, but it's something to watch out for.