A High Accuracy Transit-Time Airflow Volumetric Flowmeter Based on pMUTs Arrays

This paper describes a high-accuracy airflow volumetric flowmeter using piezoelectric micromachined ultrasound transducers (pMUTs) arrays based on the 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 $3.5\times 3.5\ \text{mm}^{2}$ , so the pMUTs-based flowmeter can conveniently measure the flow rate in small pipes. Leveraging on the high signal to noise ratio (SNR, ∼29 dB) of the pMUTs and good resolution (ns) of the evaluation board, the flowmeter has high accuracy. The relative errors of the correctional volumetric flow are within 3% for the reference flow rate in the range from 0–9 L/min in a pipe with a diameter of 10 mm.