[aprssig] Cool new sensor

KF4LVZ aprssigZbr6 at acarver.net
Tue Mar 24 23:47:14 EDT 2015

On 2015-03-24 20:39, Steve Dimse wrote:
> On Mar 24, 2015, at 11:07 PM, Scott Miller <scott at opentrac.org> wrote:
>> If it's a multi-axis magnetometer, that would probably be a better way to measure wind speed than the accelerometer.
> If it were on a rotating anemometer, the magnetometer would give you a rotation rate by comparing multiple readings to get a rate of change, but the accelerometer could give you direct readings of centrifugal force, as would the gyroscope, so those would get my vote.
> And yes, the magnetometer, accelerometer, and gyroscope are all three-axis.
>> I've been meaning to try 3D printing a clip-on cup anemometer holder for my phone.  The anemometers I've got have magnets to trip reed switches and could probably be picked up pretty easily by the phone's magnetometer.
> Interesting idea! I'd guess it would matter where the magnetometer was in the phone. Of course, I have a $10 handheld that gives me the same data and is probably the same size to carry. Maybe in a pop-up case?

A frequency analysis of one of the axes of the magnetometer would give
you rotational velocity that could be translated to wind speed.  Same
for a weather vane in a way, the output is a sinusoid (assuming the
magnet is a properly aligned bar magnet).  If it's a propeller-style
combined vane and anemometer you could use the Z-axis (vertical axis
parallel to the rotational axis of the wind vane) to measure the
anemometer propeller (sinusoid signal in Z) and then the X and Y axes
could measure the wind vane angle (quadrature sinusoids).

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