Optimisation methodology for low-g microaccelerometer

Abstract

This paper presents a single crystal silicon low-g open loop microaccelerometer designed and fabricated through a spreadsheet optimisation methodology. The paper begins with the theoretical formulation and analysis of the differential capacitive accelerometer with full-scale measurement range of ±2g and mg resolution. The "House of Quality" was then used to model and analyse the sensor design variables and device specifications qualitatively. The optimisation was implemented using the Excel Solver™ and MATLAB. The effects of electrostatic spring constant on the natural frequency and sensitivity of the accelerometer have been thoroughly discussed. The ratiometric error for this system has been optimised and is well below 2% with a cross axis sensitivity of less than 3%. The operating voltage is 5V DC. The construction is based on a hybrid two-chip design and the sensing element is wire bonded to a CMOS ASIC.