Optimization of a micro Coriolis mass flow sensor using Lorentz force actuation

Abstract

In this paper we present Finite Element models to optimize the Lorentz force actuation of a micro Coriolis mass flow sensor. These models specify six different configurations for the permanent magnets used to create the magnetic field for the actuation. The models are used to compare the various configurations in terms of the strength of the Lorentz force used for actuating the vibrational modes, and in terms of the sensitivity to misalignment of the magnetic field of the magnets. The simulations show that the Lorentz force actuation can be increased significantly by improving the placement of the magnets and that the actuation is insensitive to misalignment of the tube in relation to the magnetic field. By applying the models to a fabricated sensor, the magnetic field outside the sensor area has been reduced by 6 orders of magnitude. Due to the smaller size of the new permanent magnets, the footprint of the chip, including actuation, has been reduced by a factor 3. The models of two magnet configurations without misalignment have been validated with measurements.