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Novel piezoresistive high-g accelerometer geometry with very high sensitivity-bandwidth product

: Külls, R.; Nau, S.; Salk, M.; Thoma, K.


Sensors and Actuators. A 182 (2012), S.41-48
ISSN: 0924-4247
Fraunhofer EMI ()

This paper reports on a novel piezoresistive high-g accelerometer design, that partially overcomes a common drawback of shock sensor concepts, namely that their bandwidth, i.e. natural frequency, cannot be increased without sacrificing sensitivity. Its figure of merit (sensitivity multiplied by frequency squared) is about 5 × 10 6 m -1. This is one order of magnitude higher than in existing designs in the literature or currently on the market. The increase is made possible by a design approach that focuses on displacements rather than stresses and the utilization of a spring-mass system related parameter called the "geometrical constant". The concept allows finding initial design geometries, which can be used for further optimization, and may be applied to sensors other than accelerometers. The accelerometer design presented in this paper is implemented as a MEMS device that features self-supporting piezoresistive elements. The first specimens have been characterized for shocks of up to 75,000 × g in Hopkinson bar experiments and have sensitivities ranging from 0.035 to 0.23 V/V exc./g and natural frequencies ranging from 2.7 to 3.7 MHz. Also, measurement data from a 200,000 × g survivability check is presented.