This is the high resolution wind speed sensor based on an optical reflective interrupt sensor. The little black chip on the round sensor board is an IR transmitter / receiver pair. The white face of the interrupter wheel reflects the beam back and a pulse is created. Eight pulses per revolution provide enough resolution that within a one second capture window we can resolve wind speeds down to 0. 1 mile/h.
The mechanical parts are similar to the wind vane. A bearing housing with two ball bearings does the trick. The actual anemometer cups are replacement parts from Davis Instruments Vantage Vue station and the revolution /minute / mile of wind is known per spec. The cups are not included in the sensor kit, but can be ordered from Ambient Weather or elsewhere on E-bay for about $10 as Davis Instruments PN: 7342-178. The two halves of the housing are sealed and held together with a section of black Gorilla tape. The lower part fits directly onto a 3/4″ PVC pipe.