Wind speed calculation doesn't match data sheet

[daviesian]

The data sheet for the anemometer says that "A wind speed of 2.4km/h causes the switch to close once per second", and this library quotes the data sheet in this comment. However, the actual calculation performed doesn't match this specification. The current calculation:

ANE_RADIUS = 7  # Radius from center to the center of a cup, in CM
ANE_CIRCUMFERENCE = ANE_RADIUS * 2 * math.pi
ANE_FACTOR = 2.18  # Anemometer factor

...

wind_hz /= 2.0  # Two pulses per rotation
wind_cms = wind_hz * ANE_CIRCUMFERENCE * ANE_FACTOR
self.wind_speed = wind_cms / 100.0

Nowhere in the data sheet does it say that there are two pulses per rotation, but let's assume that you've worked that out by experimenting with the hardware.

If a wind speed of 2.4km/h gives one pulse per second, and each rotation gives two pulses, a wind speed of 4.8 km/h would result in two pulses per second, so wind_hz == 1. Let's assume that ANE_CIRCUMFERENCE is correct at $7\times2\pi = 44$ cm, and note that 4.8 km/h is 133 cm/s. Then:

$$ 133 = 1 \times 44 \times ANE\_FACTOR $$

$$ ANE\_FACTOR=\frac{133}{44}=3.02 $$

So, have you experimentally verified that the data sheet is wrong, in which case the comment in the code should probably be updated, or is the ANE_FACTOR (or ANE_RADIUS) constant wrong? I would measure the radius myself, only the kit is now a long way up on the roof of my garage :-)