Integrated thermal and micro Coriolis flow sensing system with a dynamic flow range of more than 4 decades

We have realized a micromachined single chip flow sensing system with an unprecedented ultra-wide dynamic flow range of more than 4 decades, from less than 0.1 up to more than 1000 μl/h. The system comprises both a thermal and a micro Coriolis flow sensor with partially overlapping flow ranges. Operation principle The thermal flow sensor, as shown in figure 1a, consists of a silicon nitride microchannel that is freely-suspended over an etched cavity in the silicon substrate. Two resistors, that fulfill both the heating and sensing function, are positioned on each channel segment. The resistors are connected in a Wheatstone bridge configuration. A flow through the channel results in a corresponding output voltage of the Wheatstone bridge. A Coriolis type flow sensor consists of a vibrating tube. Fluid flow inside the vibrating tube results in Coriolis forces that can be detected. The tube is actuated using Lorentz forces in a torsional mode indicated by ωam. A mass flow Φm inside the tube results in a Coriolis force Fc. The Coriolis force is capacitively detected by its induced out of plane vibration mode with an amplitude proportional to the mass flow.