Capacitive Pressure Sensor With Off-Center Elliptical Electrodes
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Solution Overview
Problem
Existing capacitive pressure sensors face challenges in maximizing deflection with minimal bending stress and detecting large pressure gradients while being easy to fabricate, particularly in maintaining accuracy and sensitivity with non-circular electrode configurations.
Innovation Solution
A capacitive pressure sensor element assembly featuring elliptically shaped electrodes, with a substrate assembly and diaphragm assembly sealed together using a frit layer, where the electrodes are fabricated off-center to allow for increased sensitivity and a smaller housing size, and a method involving printing, drying, and firing of electrodes and sealing layers to create a strong and hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If circular diaphragms with centered electrodes are used, then bending stress is minimized, but sensitivity to pressure gradients and deflection are reduced
Solution Approach 1:
The patent applies asymmetry by positioning the electrodes off-center on the diaphragm rather than at the center. This asymmetric electrode placement creates a configuration where one electrode is closer to the diaphragm edge than the other, enabling the detection of pressure gradients while maintaining acceptable stress levels through optimized geometric relationships.
2Measurement precision
If larger sensor housing is used, then electrode area and sensitivity can be increased, but device size and complexity increase
Solution Approach 1:
The patent applies local quality by concentrating the electrode area in a specific off-center location on the diaphragm rather than distributing it uniformly. This allows the electrodes to occupy a smaller total area while maintaining high local sensitivity where the pressure gradient detection is most critical, thereby reducing the overall sensor housing size.
3Measurement precision
If complex electrode configurations are used to detect pressure gradients, then measurement precision improves, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the sensor into two separate assemblies: a diaphragm assembly containing the sensing diaphragm and electrodes, and a housing assembly containing the reference electrode and electronics. This segmentation allows each assembly to be manufactured and tested independently using standard techniques, then combined through hermetic sealing, thereby simplifying the overall manufacturing process while maintaining gradient detection capability.
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 solution enhances sensitivity to pressure gradients without increasing the sensor's size, maintaining minimal bending stress and improving fabrication ease, resulting in a more accurate and robust capacitive pressure sensor.
Implementation Method 1
firing the frit of one of the assemblies prior to aligning the substrate assembly with the diaphragm assembly and fusing them together to create the sensor assembly
Implementation Method 2
capacitive pressure sensors... two electrodes. The first electrode, which responds to pressure changes, will be referred to throughout as the 'CP' electrode. The second electrode, which is the reference electrode, will be referred to as the 'CR' electrode
Data Source
AI summary
Described herein is the sense element assembly for a capacitive pressure sensor and method for creating same that has increased sensitivity without additional size. The sense element assembly and method includes fabricating an off-centered elliptically shaped center electrode, at least one elliptical annular-like electrode around the center electrode, a ground electrode and a method for fusing the layers together to optimize sensitivity.