Looking for an anemometer to build a new battery powered wireless weather station.
This type is one of the lowest priced models I can find on eBay. But is made from metal, so might be more robust and long-lasting than the flimsy plastic ones I have used in the past.
Unfortunately, the description is very badly written and the technical details are very few.
The cable terminates in a 2-pin connector. I am hoping this means that it doesn't require any external power, which is a plus for a battery powered weather station. The item description says "voltage: 0-3.8V" without saying if that is an input voltage or output voltage. I'm hoping its the output voltage and indicates that it is a "dynamo"/alternator" type which probably contains a small motor which generates a voltage when turned by the wind.
Possibly the most important figure which is missing from the description is the wind velocity which produces that maximum voltage. With that, I could at least make a crude assumption of a linear relationship between voltage and windspeed. Even better would be a graph or formula indicating the expected relationship. I'm not looking for super high accuracy.
I could calibrate it with a series of tests at different windspeeds, but obviously I would need to calibrate against something. I was considering a cheap handheld anemometer for this purpose, but it does mean extra cost:
I have also seen this type on eBay, which is plastic, but otherwise looks very similar. Despite being manufactured from plastic rather than metal, its more expensive. But at least it gives slightly more useful technical information:
My guess is that it is the "generator" type, which are in my experience nicely linear in their response.
Calibrate them by mounting off of a vehicle and driving on a windless day. The air velocity over and close to the roof will be higher than off to the side, so experiments with different mountings might be required to get an estimate of the error introduced.
Years ago I bought one at a yard sale and used it for few years with the analog meter that came with it. One day it became erratic. Upon inspection, saw the sleeve bearing on one end of the motor had worn through the brass and was rubbing steel on steel. Buyer beware!
