On cup anemometer performance analysis and improvement: a (still) ongoing process

The cup anemometer, wind speed sensor developed by T.R. Robinson in the 19th century, remains today as the best option in relation to important scientific and economic sectors such as the meteorology sector or the wind energy sector. Despite the great advances reached by new technologies as sonic anemometry, LIDAR or SODAR, the cup anemometer is the most demanded wind speed sensors thanks to its balance between accuracy, reliability, endurance and cost. In the present paper, the work carried out in relation to this instrument at the IDR/UPM Institute is briefly summarized, and then the results from the last research testing campaigns are included. The output signal of first class cup anemometers such as Thies CLIMA First Class, Thies CLIMA 4.3350, and Vector Instruments is analyzed in order to obtain insights on the instrument accuracy. It has been found that the three accelerations of the rotor are translated into a pulsed output signal that could lead to some error if that is not taken into account. Besides, the way the output signal is registered in order to correlate the output frequency with the wind speed has proven to be also a source of error.