Author Topic: Rapid updating anemometer project  (Read 394 times)

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Offline StormCapture

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Rapid updating anemometer project
« on: March 29, 2021, 08:09:54 AM »
Bit of a longshot but will see how I go.

I am wanting to create my own program that will allow me to log wind speeds at a much faster rate compared to the standard 2.5 seconds that Davis uses.  The idea came to me when I got my Peet Bros 800 and liked how it updated the wind speed every 300ms and captured gusts a lot better than the Davis when they occurred. So my plan is to have the anemometer to log wind speeds every 200-300ms and must be able to record wind direction as well.

I know this is possible seeing the Windy Palms project on the web, but any help would be appreicated, especially on the anemometer side of things and what one would be best for it. I was originally going to use a Davis 6410 anemometer but based on the formula they give V = P*(2.25/T) , for even 300ms, it'll equal 0.133 revs to equal 1mph (the conversion will be within the code) which would be practically impossibe. Am thinking of using a RM Young series anemometer which should fit the bill? I would use a Peet bros anemometer for it but cannot find much info regarding the calculations used to determine the wind speed.

Again, any help would be great

Online sky_watcher

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Re: Rapid updating anemometer project
« Reply #1 on: March 29, 2021, 04:52:45 PM »
I would use a Peet bros anemometer for it but cannot find much info regarding the calculations used to determine the wind speed.
Not sure if this will help.
In ULTIMETER Weather Stations, speed is determined by measuring the time interval between
two successive closures of the speed reed. Calibration is done as follows (RPS = revolutions
per second):

0.010 < RPS < 3.229 (approximately 0.2 < MPH < 8.2):
MPH = -0.1095(RPS 2 ) + 2.9318(RPS) – 0.1412

3.230 < RPS < 54.362 (approximately 8.2 < MPH < 136.0):
MPH = 0.0052(RPS 2 ) + 2.1980(RPS) + 1.1091

54.363 < RPS < 66.332 (approximately 136.0 < MPH < 181.5):
MPH = 0.1104(RPS 2 ) – 9.5685(RPS) + 329.87

Conversions used are: mph * 0.86897 = knots; mph * 1.6094 = kmph; mph * 0.48037 = m/s

Direction is calculated as the relative timing (phase relationship) between contact closures of the
two reed switches. This is a non-linear, sinusoidal relationship. We regard repeated actuation
of the speed reed as the reference and arbitrarily define "North" as the vane orientation that
causes the two reed switches to close at the same time. "South" is the vane orientation that
causes the direction reed to close exactly halfway between two closures of the speed reed.
“The more a man knows, the more willing he is to learn. The less a man knows, the more positive he is that he knows everything...” ― Robert G. Ingersoll