A High-Accuracy Ultrasonic Gas Flowmeter Based on Scandium-Doped Aluminum Nitride Piezoelectric Micromachined Ultrasonic Transducers

This article presents an ultrasonic gas meter based on a scandium-doped aluminum nitride (Sc0.2Al0.8N) piezoelectric micromachined ultrasonic transducer (PMUT) array, where the characteristic dimension of each PMUT cell is only $600~\mu \text {m}$ . The ultrasonic time-of-flight (TOF) difference method is employed to measure the gas flow rate, followed by ultrasonic signal processing and subsequent velocity profile and temperature compensation performed by the microcontroller. The cross correlation method is employed to detect the ultrasonic TOF difference and further suppress noise. To conduct a feasibility evaluation of the designed ultrasonic gas meter, the PMUT array, system control circuit, and ultrasonic flow channel are combined and encapsulated in a meter case. Results indicate that the ultrasonic gas meter exhibits outstanding accuracy, repeatability, and temperature adaptability. In the flow range of 0.025–2.8 m3/h, the minimum mean error and minimum repeatability error are 0.11% and 0.13%, respectively. Even when the temperature reaches 323.15 K, the designed device can achieve a mean error of no more than 0.41% with temperature compensation, which is comparable to commercialized ultrasonic gas meters. The highly reliable ultrasonic gas meter presented in this article will provide a feasible solution for advancing portable devices.