Rotating Proof Mass MEMS Pressure Sensor for Linear Differential Output
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Solution Overview
Problem
Modern tire pressure monitoring systems using MEMS pressure sensors face challenges with non-linear output signals and weak signal levels due to the inverse relationship between capacitance and distance between capacitor plates, limiting their effectiveness in accurately measuring tire pressure changes.
Innovation Solution
A MEMS pressure sensor design featuring a rotating proof mass with electrodes at both ends, generating differential capacitive output signals that provide a more linear response to external pressure changes, enhancing signal amplitude and reducing sensitivity to acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional MEMS pressure sensor with a single diaphragm and fixed electrode is used, then the device structure is simple, but the output signal is weak and non-linear
Solution Approach 1:
The single diaphragm is segmented into multiple diaphragms (first diaphragm and second diaphragm) that are coupled to the same rotating proof mass. Each diaphragm generates capacitive output from its own electrode, and these outputs are combined to produce a differential signal. This segmentation allows the system to achieve better linearity and stronger signal output while maintaining a relatively compact structure.
Solution Approach 2:
Multiple diaphragms and their associated electrodes are merged with a single rotating proof mass structure. The capacitive outputs from multiple diaphragm-electrode pairs are combined through the common rotating proof mass to generate a differential capacitive signal. This merging approach amplifies the output signal strength and improves linearity while avoiding the need for completely separate sensing elements.
2Measurement precision
If a single diaphragm capacitive sensor is used, then the device is simple to manufacture, but the signal amplitude is weak
Solution Approach 1:
The sensing element is divided into multiple diaphragms (first and second diaphragms), each with its own electrode. This segmentation multiplies the capacitive signal generation sources, resulting in a stronger overall signal amplitude. The segmented structure can be manufactured using standard MEMS fabrication techniques, maintaining ease of production.
Solution Approach 2:
Multiple capacitive sensing elements (diaphragms and electrodes) are merged with a common rotating proof mass structure. The individual capacitive signals from each diaphragm-electrode pair are combined through the mechanical coupling to the rotating proof mass, producing a differential output with enhanced amplitude. This merging strategy achieves signal amplification without requiring complex external signal conditioning circuits.
3Measurement precision
If a rotating proof mass with multiple diaphragms is used, then the differential capacitance output increases signal level, but the device complexity increases
Solution Approach 1:
Multiple diaphragms and electrodes are merged with a single rotating proof mass to generate differential capacitance output. This merging approach produces a stronger signal level by combining the capacitive effects from multiple sensing elements. The integrated design, where all components work together through the common rotating proof mass, manages complexity by avoiding separate signal processing paths for each diaphragm.
Solution Approach 2:
The rotating proof mass serves multiple functions: it acts as the common mechanical element coupling multiple diaphragms, serves as one electrode for multiple capacitive pairs, and provides the differential output mechanism. This multi-functionality reduces the need for additional components and simplifies the overall structure despite the increased sensing 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 offers a more linear and stronger signal output in response to pressure changes, improving the accuracy and reliability of tire pressure monitoring systems by using a differential capacitance output from the rotating proof mass configuration.
Implementation Method 1
measuring a differential between a first capacitance of the first variable capacitor and a second capacitance of the second variable capacitor, wherein the first and second capacitances are responsive to the first fluid pressure external to the package as applied to the diaphragm
Implementation Method 2
A MEMS pressure sensor design featuring a rotating proof mass with electrodes at both ends, generating differential capacitive output signals that provide a more linear response to external pressure changes
Data Source
AI summary
A MEMS pressure sensor device is provided that can provide both a linear output with regard to external pressure, and a differential capacitance output so as to improve the signal amplitude level. These benefits are provided through use of a rotating proof mass that generates capacitive output from electrodes configured at both ends of the rotating proof mass. Sensor output can then be generated using a difference between the capacitances generated from the ends of the rotating proof mass. An additional benefit of such a configuration is that the differential capacitance output changes in a more linear fashion with respect to external pressure changes than does a capacitive output from traditional MEMS pressure sensors.