Performance analysis of present cup anemometers

Abstract

The cup anemometer, wind speed sensor developed by T.R. Robinson in the 19th century, remainstoday as the best option in relation to important scientific and economic sectors such as themeteorology sector or the wind energy sector. Despite the great advances reached by newtechnologies as sonic anemometry, LIDAR or SODAR, the cup anemometer is the mostdemanded wind speed sensor thanks to its balance between the accuracy, reliability, enduranceand the cost. In the present paper, the work carried out in relation to this instrument at theIDR/UPM Institute is briefly summarized, and then the results from the last research testingcampaigns are included. The output signal of the first class cup anemometers such as ThiesCLIMA First Class, Thies CLIMA 4.3350, and Vector Instruments is analyzed to obtain insightson the instrument accuracy. It is found that three accelerations of the rotor are converted into apulsed output signals, leading to some error if that is not taken into account. Besides, the way theoutput signal is registered in order to correlate the output frequency with the wind speed hasproven to be also a source of error. Two ways of extracting the output frequency, namely byCounting Pulses (CP), and by using FFT are compared. Results indicate that the wind speed errorsare six times larger in the case of using FFT.