A high-resolution micro-electro-mechanical resonant tilt sensor

Abstract

This paper reports on the design and experimental evaluation of a high-resolution micro-electro-mechanical (MEM) tilt sensor based on resonant sensing principles. The sensors incorporate a pair of double-ended tuning fork (DETF) resonant strain gauges, the mechanical resonant frequencies of which shift in proportion to an axial force induced by variations in the component of gravitational acceleration along a specified input axis. An analysis of the structural design of such sensors (using analytical and finite element modelling) is presented, followed by experimental test results from device prototypes fabricated using a silicon-on-insulator (SOI) MEMS technology. This paper reports measurement conducted to quantify sensor scale factor, temperature sensitivity, scale factor linearity and resolution. It is demonstrated that such sensors provide a ±90° dynamic range for tilt measurements with a temperature sensitivity of nearly 500ppb/K (equating to systematic sensitivity error of approximately 0.007°/K). When configured as a tilt sensor, it is also shown that the scale factor linearity is better than 1.4% for a ±20° tilt angle range. The bias stability of a micro-fabricated prototype is below 500ng for an averaging time of 0.8s making these devices a potentially attractive option for numerous precision tilt sensing applications.