The Prandtl micro flow sensor (PMFS): A novel silicon diaphragm capacitive sensor for flow-velocity measurement

This paper presents the setup, operation principle, and fabrication process of a novel type of flow-velocity sensor. Like the well-known classical Prandtl tube [1], it realizes flow-velocity detection by measurement of the pressure difference between the stagnant fluid pressure in front of the sensor and static pressure in the flow around the sensor. This difference results in a deflection of a silicon diaphragm suspended boss, which serves as the counter electrode of an integrated capacitor that is directly exposed to the fluid to be measured. The main parameters influencing the sensor operation are discussed, including conclusions resulting from a CFD simulation of the flow around a tilted sensor. Results of wind-tunnel experiments confirm the sensor's operation principle.