Acceleration Sensor Shielding Electrode Pneumatic Damping
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Solution Overview
Problem
Micro-electromechanical acceleration sensors with interlocking comb electrodes face issues with damping, leading to mechanical defects and inaccurate measurements at high accelerations due to potential collisions between movable and fixed electrodes.
Innovation Solution
Incorporating shielding electrodes connected to the substrate, which provide pneumatic damping by changing the volume between the comb back surface and the shielding electrode surface, and ensuring these electrodes are at the same electrical potential as the proof mass to prevent electrostatic interference, thus enhancing damping and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If interlocking comb electrodes are used to achieve linear behavior, then measurement precision is improved, but damping is insufficient leading to mechanical defects at high accelerations
Solution Approach 1:
A damping structure is introduced as an intermediary element between the movable comb electrode and the fixed counter-electrode. This damping structure provides pneumatic damping through gas pressure forces, preventing direct collision between electrodes while maintaining the interlocking comb electrode configuration for linear measurement behavior.
Solution Approach 2:
The damping structure is positioned in advance between the movable and fixed electrodes to provide cushioning before collision can occur. This prior cushioning mechanism prevents mechanical defects by absorbing impact forces through gas pressure damping before the electrodes can collide at high accelerations.
2Reliability
If the volume between comb back surface and shielding electrode surface changes, then pneumatic damping is increased, but device complexity increases
Solution Approach 1:
The damping structure serves multiple functions: it provides pneumatic damping through volume change, acts as a mechanical stop to prevent electrode collision, and maintains the electrostatic field configuration. By combining these functions into a single structure, device complexity is minimized while achieving reliable damping.
Solution Approach 2:
The damping effect is achieved by allowing the volume between the comb back surface and shielding electrode surface to change dynamically during proof mass deflection. This parameter change (volume variation) creates pneumatic damping forces that increase with acceleration, providing adaptive damping without complex active control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The increased damping reduces the risk of mechanical defects and improves the accuracy of acceleration measurements by effectively managing the deflection movement of the proof mass, preventing collisions and maintaining linear electrostatic force over a wide range.
Implementation Method 1
suitable for increasing pneumatic damping of the proof mass during a deflection movement of the proof mass
Implementation Method 2
The moveable electrode and the counter-electrode thus form a capacitor, with a resetting voltage, which must be applied to the electrodes of this capacitor for resetting, being linear to the deflection of the proof mass over a wide range
Implementation Method 3
a corresponding voltage is applied to the electrodes, which causes the test mass to reset
Data Source
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AI summary
The invention relates to an acceleration sensor, comprising a substrate having a substrate surface and a sample mass that is movable relative to the substrate in a first direction (x) parallel to the substrate surface. The sample mass has a comb-like electrode that is movable together with the sample mass and has a plurality of teeth, which extend in the first direction (x). The acceleration sensor further comprises a counter-electrode fixedly connected to the substrate, which counter-electrode has a fixed comb-like electrode and wherein said fixed comb-like electrode has a plurality of teeth which extend in a direction opposite to the first direction (x). The teeth of the movable comb-like electrode engage with the teeth of the fixed comb-like electrode. The acceleration sensor further comprises a shielding electrode fixedly connected to the substrate and which is suitable for increasing a pneumatic damping of the sample mass during a deflection movement of the sample mass.