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Topic: Anemometer (Read 2 times) previous topic - next topic

ulrichard

May 29, 2010, 05:10 pm Last Edit: May 29, 2010, 05:48 pm by ulrichard Reason: 1
I have two Anemometers that I want to use for a small weather station:
http://flytec.ch/sensoren.htm  (has 2 wires in the cable : white, brown)
http://www.aircotec.com/cms/front_content.php?idcat=49 (has 3 wires in the cable : blue, brown, black)
Now I tried to find information on how to interface them on the internet. But I don't find any reference to something that looks similar. Some of the bigger ones say they're optical, while some seem to have reed switches, still others might be inductive.

I will contact flytec and aircotec, but it's weekend, and maybe someone on the forum can point me to the right direction before they will answer.

ulrichard

I found nothing relevant on google.

Started measuring the 2 wire one.
The voltmeter can't detect any resistance. Tested both directions. Still and rotating.

3.3V  ->  Anemometer  ->  R15K  -> GND
Measured with the ocilloscope between both ends of the anemometer.
Switched the wires of the anemometer.
No change in the voltage if it's still or rotating at different speeds.

tkbyd

Some anemometers work by closing a switch once per revolution.

Others work by using the cups to drive a little generator. The faster the wind, the more voltage produced.

And still other approaches exist... see below.

Regarding your three wire sensor: It may have an anemometer with a Hall effect sensor detecting the passage of a magnet, once per revolution. If so, that is a neat anemometer... be careful not to damage the sensor with connecting things to it. Or you may have one of the "fancy" ones.

Two esoteric approaches are used....

a) Put a voltage through a wire with a high temperature coefficient. The current will tell you how hot the wire is, the temperature of the wire will depend on...
i) How hard the wind is blowing on it.
ii) How warm the air in that wind is.

b) It is possible to have several ultrasonic trasponders "squeeking" at detectors in a small unit which measures the time taken for the sounds to travel different directions through a horizontal plane. Measurements of Doppler shifts, and some hairy geometry calculations will tell you the wind speed and direction.

Bottom line: Hope that your 3 wire sensor isn't one of the clever ones. If it is, it ought to be worth something to someone on eBay with one of the Aircotec modules!


retrolefty

#3
May 30, 2010, 06:15 pm Last Edit: May 30, 2010, 06:16 pm by retrolefty Reason: 1
Anemometer is just a generic term to mean measuring wind speed. I've seen many different methods use in projects over the years.

Use a small DC motor as a generator and measure the developed voltage to determine speed.

Use a magnetic sensor to read the spinning cups and time the rpms to determine wind speed.

Use four sensitive RTD temperature sensors along with a reference sensor (not subject to the wind) and with enough software, wind speed and direction can be calculated. No moving parts required.

Use four ultrasonic sender and receiver units and determine wind speed and directions. Again no moving parts required.

I'm sure there may be even more methods, but you get the idea.

Lefty

ulrichard

#4
May 30, 2010, 06:33 pm Last Edit: May 30, 2010, 06:54 pm by ulrichard Reason: 1
It's not so well visible on the photos, but they have a small fan inside. The word by word translation from German would be something like wing wheel, but I guess that doesn't make sense in English.
If I blow through, they keep spinning for a while. They have saphire bearings with very small resistance.
If it was a small generator, I should be able to measure something with the Voltmeter/Ocilloscope, right?

My best guess at the moment is a hall effect sensor.
The three wire device could match something like this:
http://openenergymonitor.blogspot.com/2009/09/hall-effect-sensor-circuit-diagram.html
But how would I find out which wire is which. Are there any standards?

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