Topology: A Source of Nonlinearity in the MEMS Thermal Accelerometer

Abstract

This article reports the effect of package and constituent geometries on the response linearity of a micromachined single-axis thermal accelerometer. To investigate this phenomenon, a packaged device is filled with a high-density gas inside a sealed chamber on a rotation stage, and its response is measured as its sensitive axis of acceleration is tilted relative to the Earth's gravitational acceleration g 9.81ms2 . Linearity of the response is examined compared to an analytical model describing natural convection between horizontal heated concentric cylinders. In a 360 turn, full-scale nonlinearities of 3.1 and 0.9 are measured in each half cycle. This asymmetrical performance is attributed to a lower level of geometrical symmetry in the packaged device. To compensate for the modulated response, a geometrical correction factor is introduced to the model, improving its performance prediction with a symmetrical full-scale linearity error of 0.5.