High Accuracy Time of Flight Measurement for Ultrasonic Anemometer Applications

Ultrasonic anemometer system based on new digital signal processing technique is described. The anemometer system consists of two pairs of ultrasonic transducers placed vertically for vector result. In one pair of transducers, short train of waves is transmitted from one transducer to another. The amplitude of the received waveform is an envelope which starts from zero reaches to a peak and then dies out, ultrasonic anemometer measurements are based on the determination of the time of flight (T.o.F), a common method used is threshold crossing technique, which introduces error due to the noise and piezoelectric transducer´s diverse mechanical characteristics. In this paper digital signal processing and cluster analysis is used to determine the accurate time delay. Compared to other signal processing technique such as threshold crossing. Result show the new processing technique is stable, accurate and capable in practical measurement.