A binary gas concentration and flow rate measurement system based on scandium-doped aluminum nitride piezoelectric micromachined ultrasonic transducers

This paper presents an ultrasonic binary gas concentration and flow rate measurement system (UBCFS) based on a scandium-doped aluminum nitride (Sc$0.2$Al$0.8$N) piezoelectric micromachined ultrasonic transducer (PMUT) array, enabling the simultaneous measurement of binary gas concentration and flow rate. The ultrasonic propagation time method is employed to determine binary gas concentration and flow rate. To assess the feasibility of the proposed UBCFS, it is integrated into an experimental setup composed of nitrogen (N₂) and argon (Ar) gas paths. Results indicate that the reported UBCFS measures both gas concentration and flow rate with high accuracy and repeatability. For binary gas flow rate measurements, the mean error and repeatability error are below 0.403% and 0.667%, respectively, across all binary gas concentrations. Within the concentration range of 0% to 100%, the minimum mean error and repeatability error for concentration measurements are 0.03% and 0.04%, respectively, which is almost unaffected by gas flow rate. The performance of the proposed UBCFS based on PMUT arrays surpasses that of most reported or commercialized devices. The compact, cost-effective, and highly reliable UBCFS provides a feasible solution for portable equipment utilized in binary gas detection and control in semiconductor processing.