An ultrasonic flowmeter for liquid flow measurement in small pipes using AlN piezoelectric micromachined ultrasonic transducer arrays

Abstract This paper firstly proposes an ultrasonic liquid flowmeter based on AlN piezoelectric micromachined ultrasonic transducer arrays. By detecting the transit time of ultrasonic wave, the flowmeter can measure liquid flow in small pipes (8 mm), which is difficult for traditional bulk piezoelectric ultrasonic transducers. In the flowmeter, the acoustic path and flow path are overlapped, which greatly improves sensitivity compared with the typical structure. The cross-correlation method is used to determine the ultrasonic transit time, which can effectively reduce the influence of signal noise and amplitude change. The maximum measurement error of the flowmeter is less than 5% in the flow range of 0–3.36 l min −1 .