Capacitive Pressure Sensor with Electromagnetic Shielding
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Solution Overview
Problem
Current sensors for monitoring construction structures, such as concrete buildings, are bulky, costly, prone to errors, and susceptible to electromagnetic interference and detachment due to environmental factors like humidity and air bubbles, failing to meet requirements of high accuracy, robustness, and simplicity in operation.
Innovation Solution
A capacitive pressure sensor with a flat parallel plate design, utilizing copper and glass ceramic layers, and a dielectric layer, integrated with a screen electrode for electromagnetic shielding, and brackets for secure adhesion, allowing for accurate detection of compressive and tensile stresses while resisting interference and detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensors are used for monitoring construction structures, then measurement capability is provided, but the sensors are bulky, costly, and complex to operate
Solution Approach 1:
The patent replaces traditional mechanical strain gauges and extensometers with a capacitive sensing system. The sensor uses capacitive electrodes that detect stress through changes in capacitance values, eliminating the need for complex mechanical measurement components and their associated wiring and signal conditioning circuits.
Solution Approach 2:
The patent changes the measurement parameter from mechanical deformation to electrical capacitance. By monitoring capacitance variations between electrodes embedded in the concrete structure, the system detects stress states without requiring mechanical contact or complex mechanical sensing mechanisms.
2Measurement precision
If sensors are embedded in the structure to be monitored, then direct measurement is achieved, but the sensors become subject to humidity and other factors which falsify results and reduce operational life
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the capacitive electrodes and the concrete structure. This layer protects the electrodes from direct contact with moisture and corrosive environmental factors while still allowing capacitive coupling to detect stress-induced changes in the concrete's dielectric properties.
Solution Approach 2:
The patent uses the concrete structure itself as part of the sensing mechanism. The concrete acts as one of the capacitive plates, and stress changes in the concrete directly modulate the capacitance between the embedded electrodes and the concrete surface, eliminating the need for separate mechanical sensing elements that could fail.
3Measurement precision
If sensors are positioned in the structure, then direct stress monitoring is achieved, but positioning is critical and sensors may become partially detached due to sand, grit or air bubbles
Solution Approach 1:
The patent replaces mechanical bonding requirements with electromagnetic field-based sensing. The capacitive electrodes detect stress through changes in the dielectric properties of the concrete, eliminating the need for mechanical adhesion and complex positioning procedures. The sensing mechanism works through the concrete matrix itself rather than requiring direct mechanical contact.
Solution Approach 2:
The patent changes from mechanical measurement requiring precise physical contact to electrical measurement through capacitance changes. This allows the electrodes to be embedded without critical positioning requirements, as the capacitive field penetrates the concrete and detects stress-induced dielectric changes regardless of minor variations in electrode placement.
4Measurement precision
If sensors are used in construction environments, then stress monitoring is provided, but electromagnetic interference from electrical machines falsifies detection results
Solution Approach 1:
The patent uses the concrete structure as an intermediary medium for signal transmission. The capacitive sensing mechanism detects stress through changes in the concrete's dielectric properties, and the concrete itself acts as an isolating medium that blocks external electromagnetic interference from reaching the sensing electrodes.
Solution Approach 2:
The patent measures the electrical properties of the concrete structure directly rather than using separate electronic sensors susceptible to interference. By detecting stress-induced changes in the concrete's own dielectric characteristics, the system inherently rejects external electromagnetic noise that does not couple with the concrete's electrical properties.
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 capacitive pressure sensor provides high measurement accuracy, robustness, and immunity to electromagnetic interference, ensuring reliable monitoring of stresses in construction structures with ease of positioning and operation, capable of detecting pressures up to hundreds of atmospheres.
Implementation Method 1
a detection capacitor C with flat parallel faces, the plates of which are defined by said first and second plate layers (4a, 4b) is formed within itself, and a dielectric layer (6) is disposed between said first and second plate layers (4a, 4b) so as to form a detection capacitor C
Implementation Method 2
The capacitive pressure sensor (1) further comprises a screen electrode (S), which screens the detection capacitor (C) against electromagnetic interference
Data Source
Figure 1A~2
Figure 3A~4
Figure 5~6C
AI summary
A capacitive sensor (1), for monitoring stresses acting in a construction structure when introduced into the construction structure, has a multi-layer structure provided with an upper conductive layer (2a), defining an upper outer surface of the sensor; a lower conductive layer (2b), defining a lower outer surface of the sensor; at least a first layer (5a) of insulating material, in contact with the upper conductive layer; at least a second layer (5b) of insulating material, in contact with the lower conductive layer; at least a first plate layer (4a), of conductive material; at least a second plate layer (4b), of conductive material; at least one dielectric layer (6), interposed between the first plate layer and the second plate layer to define at least one detection capacitor (C) inside the multi-layer structure of the sensor; wherein the upper and lower conductive layers are designed to jointly define an electromagnetic screen for screening the detection capacitor against electromagnetic interference originating from outside the capacitive sensor.