一种低信噪比的超声波飞行时间测量方法OA

In order to solve the inaccurate positioning of feature points and low accuracy resulted from the high noise in echo,A low sig-nal-to-noise ratio(SNR)ultrasonic time-of-flight measurement method is proposed.The empirical wavelet transform is used to decompose the low-frequency sampled echo signal adaptively.The noise reduction and reconstruction of the echo are realized according to the corre-lation between the decomposition component and the original signal.Subsequently,the similarity of waveforms is evaluated by computing the cosine distance between the reference echo and the reconstructed echo and the echo characteristic peak is determined.Finally,the new data sequence is composed of the mapping data of reference echo data and the reconstructed echo data at the characteristic peak.The echo characteristic point is located by the data sequence and the accurate measurement of flight time is obtained.The experimental results show that the echo feature points are located accurately and the time of flight is measured accurately at low sampling rate.The performance of the field ultrasonic flowmeter is effectively improved.