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Proceedings Paper

Comparison between an optical and a capacitive transducer for a novel multiaxial bulk-micromachined accelerometer
Author(s): Gerold Schropfer; Michel de Labachelerie
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Paper Abstract

Recently, we demonstrated the feasibility of a novel 3D silicon bulk-micromachined accelerometer with an optical or a capacitive read-out. In this paper we will compare both detection techniques, and also show their potentials and limitations. The mechanical elements of the accelerometers are fabricated by an unconventional wet etching process of (100) silicon, resulting in symmetrically suspended seismic masses with a high lateral sensitivity and very low transverse sensitivities. For the detection of the seismic mass displacement under the effect of an acceleration, two possibilities are investigated. Firstly, by forming a Fabry- Perot cavity between the seismic mass and the output of an optical fiber, the acceleration can be sensed by measuring the optical path change. Secondly, comb shaped electrodes have been implemented to form a capacitive transducer. Both techniques can be used to build a 3D accelerometer system. Finally, we show that the noise floors of both devices are on the same order of magnitude, leading to a potentially high sensitivity (down to 1 (mu) g/(root)Hz). The optical device shows the advantage of multiplexing capability, passive fiber alignment, distant read-out, and immunity to electromagnetic interference. The capacitive transducer has beside the general advantages of an electrostatic transducer (such as possible closed loop-operation, wide temperature range, low power operation) a linear capacitive change versus displacements.

Paper Details

Date Published: 8 September 1998
PDF: 11 pages
Proc. SPIE 3514, Micromachined Devices and Components IV, (8 September 1998); doi: 10.1117/12.323887
Show Author Affiliations
Gerold Schropfer, Univ. de Franche-Comte (France)
Michel de Labachelerie, Univ. de Franche-Comte (France)

Published in SPIE Proceedings Vol. 3514:
Micromachined Devices and Components IV
Patrick J. French; Kevin H. Chau, Editor(s)

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