A MEMS Coriolis Mass Flow Sensing System with Combined Drive and Sense Interface
A. C. De Oliveira (TU Delft - ChemE/Delft Ingenious Design)
T. V.P. Schut (University of Twente)
J. Groenesteijn (University of Twente)
Q. Fan (University of Twente)
R. J. Wiegerink (University of Twente)
K. A.A. Makinwa (TU Delft - Microelectronics)
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Abstract
This paper describes an interface circuit for a MEMS Coriolis mass flow sensor that combines both drive and sense circuitry. The MEMS sensor consists of a suspended resonant tube, which is read-out by comb capacitors and driven into oscillation by current flowing through a drive coil in a magnet field. The interface circuit comprises a low-noise front-end that performs capacitance-to-voltage (C/V) conversion, and a drive-loop with automatic amplitude control. Drive motion can also be detected from the output of the front-end, allowing both drive and sense functions to be combined. The front-end is chopped to mitigate its 1/ f noise. When implemented with commercial off-the-shelf (COTS) components, the proposed interface draws 250 mA from a single 5-V supply. Mass flow measurements with Nitrogen gas (N2) show that the sensor's drive frequency drifts by less than 1 mHz (rms) per hour, while its zero stability is less than 2.6 mg/h during an 80s measurement.