This sensor is slick!
A hall effect array sensor and a rotating magnet provides for a completely friction less wind direction sensor. A diametrically polarized magnet is held in the bottom of the vane shaft and a pair of ball bearings in the housing make the vane spin completely freely. Built into the sensing chip are 4 separate Hall sensors that measure the direction and strength of the magnetic field from the magnet on the shaft. The built in logic then calculates the absolute position of the magnet in respect to its case and resolves the rotation into 256 steps. The result can be read as an analog voltage increasing from 0-360 degree.
The first prototype of this sensor is still in use after more than 5 years of nearly constant movement by the wind.
The picture shows the housing with a Davis Instrument vane attached.The two halves of the housing are sealed and held together with a section of Gorilla tape. The lower part fits directly onto a 3/4″ PVC pipe.
I have transitioned to the mechanical movements from Inspeed now for both wind sensors since obtaining the vane and cups from Davis Instruments proved to be a real pain. The same electronics is used in the Inspeeds mechanisms and there is a 3/4″ PVC pipe adapter available for mounting. See the download section for specs.