sensors & using them for something useful

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Gyro. • Theory. • structures. • Gas. • Resistive/capacitive, thin/thick film .... Spring_2007_MEMS_JKa.ppt / 2007-03-07. Company Confidential. Gyros… • Vibrating ...
Microelectromechanical(-ish) sensors & using them for something useful S-108.4010 Licentiate course in measurement science and technology JKa 07.03.2007

Company Confidential 1

© 2007

Spring_2007_MEMS_JKa.ppt / 2007-03-07

“MEMS-like” sensors • MEMS general • Displacement • Capacitive • Basic equations

• Resistive

• Properties • Inertial • Acceleration • Bulk • surface

• Angular acceleration • examples

• Gyro • Theory • structures

• Gas • Resistive/capacitive, thin/thick film • Fabry perot • Combination Company Confidential 2

© 2007

Spring_2007_MEMS_JKa.ppt / 2007-03-07

MEMS inertial sensors

movement

• Simple pendulum analogy • Inertia Ædeflection • Properties: • Spring constant • Mass

Bandwidth etc.

• Damping

mass deflection

Company Confidential 3

© 2007

Spring_2007_MEMS_JKa.ppt / 2007-03-07

Capacitive measurement • Movement detected as a change in capacitance (Si~ideal spring) • Plate capacitor: C~ A, 1/d • Noise limits resolution

• Base capacitance can be increased by • Increasing surface area A • Decreasing electrode separation d • Paralleling several plate capacitors

A d

ε C

Company Confidential 4

© 2007

Spring_2007_MEMS_JKa.ppt / 2007-03-07

Linear acceleration sensor • Inertial mass • Spring(s) • Mass position measured • capacitively

C1

C1

C2

C2 C1

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