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### Wind sensor formula for mph

Posted: Thu Jun 14, 2012 12:51 pm
I'm using an Arduino Uno board with the wind sensor hooked up to an analog pin. Does anyone know a formula for converting the analog reading into a number in kmh or mph?

I'm also curious (if the above formula does exist) if one is known that accounts for changes in temperature.

Thanks

### Re: Wind sensor formula for mph

Posted: Sat Jun 16, 2012 4:29 pm
I am sure there is data curve out there for the specific sensor... I'm sure there is calibration required per unit... , you can derive your own pretty easy.. depending on your needed level of accuracy.

Solicit help from a friend, have them hold the working sensor out your car window. Record sensor readings in increments of 10 mph... from that data plot, you can derive a reasonably accurate wind speed to analog out curve...

Would be interesting to compare the short wind gust curve to a prolonged sustained wind curve... I'd expect a slight difference..

If you do it, post it... I'm looking at adding that sensor soon as well...

### Re: Wind sensor formula for mph

Posted: Mon Aug 20, 2012 2:48 pm
I'm getting a \$30 hand-held anemometer to try to calibrate this sensor. I'll try to derive a formula for a given extreme position of the trimpot (max counter clockwise or max clockwise) where temperature and Voltage are input and wind speed is output. I'll post it if I'm successful.

### Re: Wind sensor formula for mph

Posted: Thu Aug 23, 2012 3:05 pm
I have gathered a lot of data, but I have found no clear pattern. In fact, some of the data at similar temperature shows less Voltage being used at higher wind speed. Will try varying my test environment next.

### Re: Wind sensor formula for mph

Posted: Mon Aug 27, 2012 2:16 pm
On Arduino, I'm starting to think that this device is a better wind detector than it is a wind speed meter. I can easily tell the difference between some wind and no wind, for normal-range room temperature and for *most* trimpot positions (270 degrees seemed to always output the same value +/- 0.1%, but 0, 90, and 180 were good). When it comes time to tell one speed apart from another, the test data set doesn't support it. I got higher Out values (at the same temperature) for slower air than I do for faster air.

Here's some of my data that shows the inconsistency. I used a hand-held anemometer to get reference wind speeds at fixed points from a hair dryer's output vent, and I measured the wind sensor's Out at those pre-measured distances, reporting the average value over 100 samples, after a 10s warmup period. I'm supplying 9V external power to the Arduino and powering the wind sensor off its regulated 5V pin.

Code: Select all

``````avg Out reading   humidity%   temperature in C   wind speed m/s	   trimpot in deg   Arduino PSU V
021.02                34.00	     29.84			0.0                      90                    9
206.31                33.00	     29.00			4.0                      90                    9
197.62                33.00	     29.00			5.0                      90                    9
214.49                33.04	     28.96			6.0                      90                    9
``````
I can't fit this data to any function that I can use to determine wind speed. Am I doing something fundamentally wrong, or is this wind sensor not a true anemometer?

### Re: Wind sensor formula for mph

Posted: Mon Aug 27, 2012 2:46 pm
Human,

It has a log function. It's not linear. The voltage is proportional the square root of wind speed.
BUT -

It varies with ambient temp - values go up with colder ambient.
It varies a little over 10% with sensor orientation to the wind.

Varying the pot is not going to be too useful. Just set it a fairly low number with no wind (we use .5V) and go from there.
So it's not a true anemometer in the sense of being really useful (in its current state) for quantifying wind speed.
I do agree with that.

Paul

### Re: Wind sensor formula for mph

Posted: Mon May 20, 2013 3:30 pm
I have the same question. I am using the RAW output from the sensor to measure wind speed from a fan.

I do not need much precision and dont really need to compensate for temperature.

However it would be nice if the output was somewhat related to MPH or m/s rather than just the analog output (0 to 1023) from the arduino.

So I understand its a logarithmic output proportional to the square root of wind speed.... but not being a math guy... how do I convert it to meters/second? (again keeping it mind I dont really care for high accuracy)

Just pointing me in what math has to be applied, then I can fine tune it from there.

Thank you
Med

### Re: Wind sensor formula for mph

Posted: Sat Feb 22, 2014 10:10 pm
Does anyone have a simple arduino sketch of the wind sensor outputting usable values, such. Wind speed, and temp?

I'm building a synth with the hope to include a wind controller for handling note on and sustain and stop. So far the vales I'm getting don't seem to be correct, looking to see how other are getting workable values.

### Re: Wind sensor formula for mph

Posted: Tue Sep 01, 2015 10:47 am
Hi

last week I got two of your wind sensors (both revisions). I want to meaure true wind speed on my bike. Because I also measure altitude (with a BME280 pressure sensor) I have a very accurate temperature reading in degrees C from this source. I think, this could avoid many problems with the calibraton of the NTC resistor.
Now my question: Do you have a formula where I can use the (known) temperature in Celsius to calculate wind speed? Did anybody else try this procedure?

Andreas

### Re: Wind sensor formula for mph

Posted: Mon Sep 25, 2017 11:27 am
Hi...i am a new user here. In my case some of the data at similar temperature shows less Voltage being used at higher wind speed. Will try varying my test environment next.

### Wind sensor formula for mph

Posted: Thu Oct 12, 2017 5:10 am
Hi list,
how accurate is the Lux reading obtained with the Lux-Sensor in Open Signals?
Best
Alex