Highly Accurate Airflow Volumetric Flowmeters via pMUTs Arrays Based on Transit Time

Abstract

This paper describes a highly accurate airflow volumetric flowmeter using piezoelectric micromachined ultrasonic transducers (pMUTs) arrays based on transit time. Two pieces of 10by10 multipled aluminum nitride (AlN) pMUTs arrays at resonant frequency of 980 kHz are employed to transmit and receive ultrasonic signals alternately. The dimension of the fabricated 10by10 array is about $3.5 \times 3.5$ mm2, so the pMUTs-based flowmeter is able to measure flow rate in a 3D-printed pipe with an inner diameter of 10 mm. An evaluation board TDC1000-TDC7200EVM with resolution in ns is used to excite the transducers and handle the received signal. Leveraging on the high signal to noise ratio (SNR, ~29dB) of the pMUTs array and excellent resolution (ns) of the evaluation board, the flowmeter has high accuracy. For the reference volumetric flow rate varying from 0–9 L/min in the range of laminar flow, the relative errors of the correctional volumetric flow are within 3%.