A Single PMUT-Based Sensing System for the Simultaneous Measurement of Liquid Level and Concentration

This paper presents a miniaturized sensing system utilizing a single scandium-doped aluminum nitride (ScAlN) piezoelectric micromachined ultrasonic transducer (PMUT) chip to simultaneously detect two important liquid parameters, level and concentration. Here, a single <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.8\ \text{mm} \times 2.8\ \text{mm}$</tex> PMUT chip serves as the sensing unit, enabling the detection of two liquid parameters through a custom-designed package. In comparison to previously reported work, the sensor system proposed here offers significant advantages in terms of low cost, miniaturization and integration.