Spring 2012 Conference
March 7 - 9
Three axis Lorentz Force Magnetic Sensor
We present a low-power three axis MEMS magnetic sensor suitable for use as an electronic compass in smart phones and portable electronics. Our objective is to achieve a resolution of 200 nT/rt Hz and power consumption of 5mW/axis with DC power supply of 3.3V. Experimental results show that with 0.58 mW used to provide the two-axis excitation current, the sensor's resolution is 137 nT/rt Hz for z-axis magnetic field inputs and 444 nT/rt Hz for x- and y-axis fields. For z-axis field measurements, Brownian noise is the dominant noise component, while x- and y-axis field measurements are limited by the electronic noise in the discrete capacitive sensing electronics. The major source of offset error is residual motion induced by electrostatic force. The residual motion can be reduced by applying a DC compensation voltage to null the electrostatic force.