The Research On Ultrasonic Flow Measurement Algorithm Based On ApFFT

In ultrasonic flowmeter,the key to measuring the flow is the transmission time of ultrasonic signal,due to the fact that the first wave of the received signal cannot be determined,causing inaccurate pulse count and time measurement,the Half segment phase difference algorithm and Double segment phase difference algorithm based on the principle of phase measurement for ApFFT algorithm are proposed.Their basic idea is to convert the measurement of time into phase,then according to the relationship between the phase difference and the time difference of the forward and reward signals in ultrasonic flowmeter to derive flow.In the actual experiment,when the fundamental frequency of the ultrasonic flowmeter is 1 MHz,the sampling frequency is 12.5 MHz,the number of sampling points is 507 and the A/D quantization bit is 11,collecting the ultrasonic large-flow data,static water data,interference data and full-wave data respectively.Because the collected flow data itself contains noise,in order to eliminate the influence of noise on the phase measurement,adopting the wavelet packet coefficient zero denoising method.For the denoised flow data,calculating the phase difference by using the Data extension correlation algorithm,ApFFT phase difference algorithm,the Half segment phase difference algorithm and Double segment phase difference algorithm respectively,the experimental results show that the Half segment phase difference algorithm and Double segment phase difference algorithm proposed in this paper can effectively reduce the measurement error of the phase difference,thus the measurement accuracy of time difference is higher,in comparison,the Double segment phase difference algorithm has higher measurement accuracy of phase difference.Figure 25,Table 9,Reference 58...