Inertial Sensor Conductive Track Width Reduction
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Solution Overview
Problem
Inertial sensors with piezoelectric quartz plates experience disturbances in measured current due to parasitic currents generated by conductive tracks near deformation zones, leading to saturation and malfunction when subjected to acceleration.
Innovation Solution
Conductive tracks in the excitation circuit are narrowed to less than 50 μm in width and spaced closer than 100 μm to minimize disturbing currents, with optimal dimensions between 5 μm and 20 μm width and 10 μm to 50 μm spacing to reduce parasitic effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conductive tracks are made wider and spaced further apart, then signal strength and electrical connectivity are improved, but disturbing currents increase causing measurement errors and sensor saturation
Solution Approach 1:
The patent applies different track width specifications to different zones of the piezoelectric plate. In critical zones where deformation occurs (bridges and decoupling frame), conductive tracks are narrowed to less than 50 μm to minimize disturbing currents. In non-critical zones, standard wider tracks can be used to maintain signal strength. This local differentiation resolves the contradiction by optimizing each zone for its specific functional requirements.
Solution Approach 2:
The excitation circuit is segmented into multiple conductive tracks with different width characteristics based on their location. The patent divides the plate into critical zones (where deformation occurs) and non-critical zones, assigning different track width specifications to each segment. This segmentation allows the system to simultaneously maintain electrical connectivity in non-critical zones while minimizing disturbing currents in critical zones.
2Object-generated harmful factors
If conductive tracks are narrowed to reduce disturbing currents, then measurement accuracy improves, but electrical conductivity and signal strength deteriorate
Solution Approach 1:
The patent ensures that narrowed conductive tracks (less than 50 μm) are placed only in critical zones where deformation occurs and disturbing currents are generated. In non-critical zones, standard width tracks are used to maintain adequate signal strength and electrical connectivity. This local quality approach ensures reliability is maintained where needed while reducing harmful effects where they occur.
Solution Approach 2:
The patent uses the spatial distribution of conductive tracks as an intermediary solution. By strategically placing narrowed tracks only in critical zones and maintaining standard width tracks in non-critical zones, the system mediates between the need to reduce disturbing currents and the need to maintain electrical connectivity. The decoupling frame and bridge structures also act as intermediaries to isolate deformation effects from the excitation circuit.
3Device complexity
If conductive tracks are placed closer together, then circuit complexity is reduced and manufacturing is simplified, but parasitic capacitive effects increase reducing measurement accuracy
Solution Approach 1:
The patent applies different spacing requirements to different zones. In critical zones, tracks are spaced less than 100 μm apart to minimize disturbing currents, accepting the parasitic capacitive effects as a necessary trade-off. In non-critical zones, tracks can be spaced further apart to reduce parasitic effects. This local differentiation resolves the contradiction by optimizing each zone for its primary requirement.
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
This configuration significantly reduces disturbing currents, enhancing the accuracy of acceleration measurements by minimizing interference and preventing sensor malfunction.
Implementation Method 1
The excitation circuit is supplied with an alternating current causing, by a piezoelectric effect, the setting in vibration of the vibrating member according to a natural frequency of vibration of this vibrating element
Implementation Method 2
When the sensor is subjected to an acceleration, the mass exerts on the vibrating element a force which modifies the frequency of vibration
Data Source
Figure 1~2
AI summary
The inertial sensor comprises a piezoelectric plate in which is delimited a vibrating member carrying excitation electrodes connected to an excitation circuit comprising conductive tracks carried by the piezoelectric plate, the excitation circuit comprising a portion of the disturbance circuit (13) in which two conductive tracks (11) extending on either side of a median plane (M) have a width (l) less than 50 µm, and preferably 10 µm, and are spaced by a distance (d) less than 100 µm, and preferably 40 µm.