Optimization of Lorentz-force MEMS magnetometers using rarefied-gas-theory

We review the design of Lorentz force-based magnetometers to be employed in MEMS inertial measurement units. Taking into account the constraints of an industrial MEMS technology already used for accelerometers and gyroscopes, it has been recently shown that standard designs have intrinsic limitations. E.g. in the classical magnetometer operated at resonance where two parallel current carrying springs are connected by a central shuttle on which sensing parallel plates are mounted, the sensitivity does not depend on the number of plates and is limited to typical values around 1aF/(μT mA) at 1mbar. In this paper two solutions have been investigated: springs have been used for both actuation and sensing, with no sensing plates; exploiting better knowledge of rarefied gas dynamics, new stators have been designed. The combination of these factors has increased the sensitivity to 4.5aF/(μT mA) at 1mbar as predicted by numerical models and verified in experiments.