The sensor used for wind speed measurement is the IMD make three cup anemometer. The sensor is basically an alternating voltage generator using a six pole magnet as the rotor and a suitable stator coil winding. The frame carrying the three cups spaced at 120 deg. rotates the anemometer rotor shaft with the wind, thereby inducing alternating voltage in the stator coils. The frequency of the alternating voltage output of the anemometer can be calculated using the relation
F=N.P/120The rpms values of the AC voltage output of the anemometer generator varies linearly with speed over a range of 0-100 Knots. The rpms versus wind speed and output voltage versus rpm are linearly related. The output of the anemometer at a wind speed of 80 Knots is 7.6 V AC corresponding to an rpm of 760.
