Research On Multi-channel Ultrasonic Doppler Flowmeter Based On Cross-correlatio

In the field of flow measurement,the ultrasonic Doppler flowmeter has outstanding performance because of its high resolution,fast response,and non-contact measurement.In recent years,with the rapid development of my country’s economy,traditional ultrasonic Doppler flowmeter are widely used in industrial and agricultural production.However,its measurement accuracy and stability cannot be better satisfied by production requirements.Thus,it has important research significance for the ultrasonic Doppler flowmeter to improve the measurement accuracy and raise the lower limit of the measurement.The working principle of ultrasonic flowmeter,the research status at home and abroad,the digital signal processing technology are understood by consulting related materials and literature.In addition,considering the advantages of ultrasonic in measurement,the design scheme of the multi-channel ultrasonic Doppler flowmeter is based on the traditional ultrasonic Doppler flowmeter.Therefore,in order to achieve the purpose of industrial production measurement standards,the ultrasonic Doppler flowmeter has been improved in terms of hardware structure and data processing algorithm,which enhances the measurement accuracy of the ultrasonic Doppler flowmeter and expands the measurement range.On the hardware structure,the ultrasonic signal is collected by multiple channels to avoid the shortcomings of traditional single-channel collection of signals.At the data processing part,the acquired signal is processed by FFT spectrum analysis and multiple cross-correlation in the time domain and frequency domain,which causes the noise interference in the acquired signal to be filtered out.First of all,in the frequency domain signal,the frequency range of the current signal is obtained by the FFT spectrum analysis method.Then,the signal is collected by multiple channels at appropriate time intervals.Finally,in the time domain,noise interference in multiple sets of data is filtered by multiple crosscorrelation algorithms to obtain a Doppler frequency shift signal,which is improve the signal-to-noise ratio of the signal.As a matter of fact,through simulation experiments,it is known that the combination of FFT spectrum analysis and multiple crosscorrelation has certain advantages in processing noise interference.The hardware circuit is based on the STM32F103 microprocessor,which is composed of ultrasonic signal transmitting and receiving circuits,A/D acquisition circuits,ultrasonic signal processing circuits and other peripheral circuits.The functions of signal mixing,filtering and amplification are provided by the ultrasonic signal processing circuit.The peripheral circuit is made up of key control,liquid crystal display and communication transmission.Meanwhile,the software program is formed of A/D data conversion,digital signal processing,key scanning,liquid crystal display and data communication.During the indoor liquid flow experiment platform,the design scheme is verified by experiments.In different flow rate environments,the experimental measurement results are recorded.Compared with the measurement results of the 0.5 grade standard meter and single channel ultrasonic Doppler flowmeter,it is found that the proposed design can effectively improve the signal-to-noise ratio of weak-intensity signals in strong background noise and enhance the measurement accuracy.At the same time,the measurement effect is significant at low flow rates,and the measurement lower limit is validly extended.Lastly,the design plan has met the expected requirements.