Electrical & Computer Engineering     |     Carnegie Mellon

Tuesday, October 16, 12:15-1:15 p.m. HH-1112


Amy Wung
Carnegie Mellon University

Tri-axial High-G CMOS-MEMS Capacitive Accelerometer Array

Military and industrial applications, such as vehicle crash and safety testing, require inertial sensors capable of measuring accelerations up to 20,000 g's, where 1 g = 9.8 m/s2. Piezoresistive and piezoelectric high-g MEMS sold commercially by Endevco, have demonstrated a sensitivity range of ±2,000 g's [1] and higher. The noise limit of these accelerometers due to the mechanical and electrical thermal noise of the sensor is low [2]. However piezoresistive accelerometers are not integrated with the sense electronics on a single chip, introducing interconnect parasitics between the sensor and electronics. The CMOS-MEMS solution has the advantage of lower parasitics due to single-chip integration, increasing the sensitivity-to-noise ratio. A tri-axial high-g integrated CMOS-MEMS capacitive accelerometer has been designed and tested.

The high-g accelerometer capacitive design is a new derivative of previous work at Carnegie Mellon on low-g integrated accelerometers. The structure of this high-g accelerometer departs from traditional low-g plate and comb drive capacitive sensing accelerometers, instead taking the form of an array of cantilever structures. The cantilever's reduced mass and increased stiffness increases the sensitivity range to the desired 20,000 g's. An array of cantilever structures is electrically connected in parallel to obtain larger capacitance sensitivity.

The design methodology presented will demonstrate the theory and simulations used to optimize the cantilever mechanical structure and the sense capacitors. Performance characteristics calculated from theory and simulation will be compared to piezoresistive accelerometer performance data given by Endevco. The noise limit of both the CMOS-MEMS capacitive accelerometer array and piezoelectric accelerometers will be compared. Preliminary shock testing results in the 100-250 g range will be presented.


Amy Wung is currently a Ph.D. student in the Electrical and Computer Engineering Department at Carnegie Mellon University. She received her B.S. from University of California, Berkeley in 2004. Her research interests include MEMS inertial sensors and nonlinear parametric oscillators. She is currently an NSF graduate research fellow.