A MEMS Coriolis Mass Flow Sensing System with Combined Drive and Sense Interface
A.C. Oliveira Alves (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.