Capacitive and Piezoelectric Pressure Sensor with Silicon Membrane
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Solution Overview
Problem
Existing electromechanical fluid pressure sensors for aeronautical applications are bulky, expensive, sensitive to temperature variations, and require frequent calibration, with manual assembly and sealing operations leading to reliability issues and high production costs.
Innovation Solution
A pressure measuring device combining a capacitive and a piezoelectric sensor on a common support, with the capacitive sensor facing the fluid and the piezoelectric sensor internally filtered, allowing for automated assembly, reduced thermal sensitivity, and remote calibration through wireless communication, and using protective coatings for environmental resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric pressure sensor with transfer fluid duct is used, then pressure measurement capability is achieved, but device size and weight increase
Solution Approach 1:
The patent extracts and eliminates the transfer fluid duct and sealing elements from the sensor structure. By directly exposing the piezoelectric sensor to the fluid pressure, the bulky duct system is removed, significantly reducing device size and weight while maintaining pressure measurement capability.
Solution Approach 2:
The patent uses a thin silicon membrane as a pressure transmission interface instead of a bulky duct system. This thin film allows direct pressure transmission to the sensor while minimizing structural volume and mass.
2Reliability
If transfer fluid is used to transmit pressure, then pressure measurement is enabled, but thermal sensitivity and temperature-induced errors increase
Solution Approach 1:
The patent removes the transfer fluid entirely from the system. By eliminating the fluid medium, all temperature-induced effects on the fluid (expansion, congealing, viscosity changes) are eliminated, directly resolving thermal sensitivity issues.
Solution Approach 2:
The patent introduces a solid silicon membrane as an intermediary between the pressure source and sensor, replacing the liquid transfer fluid. This solid intermediary is less sensitive to temperature variations and eliminates fluid-related thermal problems.
3Reliability
If manual assembly and sealing operations are used for sensor construction, then tight sealing is achieved, but production cost and assembly time increase
Solution Approach 1:
The patent merges the pressure sensor construction with the substrate fabrication process using MEMS technology. The silicon membrane and sensor elements are created in an integrated manner through semiconductor manufacturing processes, eliminating separate manual assembly and sealing operations.
Solution Approach 2:
The patent replaces manual mechanical assembly operations with automated semiconductor fabrication processes. The complex sealing and assembly tasks are substituted by precision manufacturing techniques that are inherently more controllable and faster.
4Measurement precision
If resistive sensors are used for pressure measurement, then pressure sensing is achieved, but regular calibration is required to maintain accuracy
Solution Approach 1:
The patent changes the sensing principle from resistive to piezoelectric capacitance measurement. This parameter change in the measurement mechanism inherently reduces thermal sensitivity and drift, eliminating the need for frequent calibration while maintaining high accuracy.
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 reduces costs, improves reliability and precision, and minimizes downtime by enabling real-time calibration and fault detection, while reducing thermal sensitivity and environmental susceptibility.
Implementation Method 1
piezoelectric strain gauges mounted as a Wheatstone bridge
Implementation Method 2
a pressure sensor of a first type which is of the capacitive type
Data Source
Figure 1
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AI summary
A pressure-measuring device (1) comprising a pressure sensor of a first type (2) and a pressure sensor of a second type (3) different to the first mounted on a common support (6) in order to be subjected to a same pressure, in which the pressure sensor of the first type (2) is a capacitive sensor, characterised in that the pressure sensor of the first type (2) comprises at least one membrane (26) and a first inner channel (30) passing through the common support (6), a second inner channel (33) for conveying a fluid to the membrane (26) being in fluid connection with the first inner channel (30). A calibration method associated with the device (1).