Ultrasonic flowmeter based on voltage-amplitude
DONG Deng-hui，BAO Min，ZHENG Xi-bin
（Faculty of Mechanical Engineering & Automation，Zhejiang Sci-Tech University，Hangzhou 310018，China）
Abstract：Aiming at the matter of fluid measurement in the unstable flow field，amplitude modulation was used to generate excitationsignals of ultrasonic sensors，then the amplitude changed feature points of received signals was detected to locate the waveform，based onthe transit time determined by zero-crossing detection of ultrasonic flowmeter. Aiming at the unstable waveform caused by the unstableflow velocity in the flow field，median filtering method was used to eliminate caused errors. In order to avoid the transit time measurement
error caused by the restriction of the ADC digits and conversion rate，the transit data was collected from analog waveform by zerocrossingdetection ，based on the feature points determination of the digital waveform. The results indicate that this measure is certainfeasible，could process and locate the ultrasonic pulse sequence accurately，the measurement error could be controlled below 1.5%，it canachieve the requirement of the secondary standard of precision.
Key words：ultrasonic；flowmeter；amplitude；zero-crossing detection；transit time