Capacitance Sensor with Elastomer Dielectric for Noise Reduction
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Solution Overview
Problem
Conventional capacitive sensors experience significant fluctuations in measured capacitance due to environmental factors such as electromagnetic noise and proximity to conductors, which can lead to inaccurate measurements, especially when the sensor sheet is exposed or in contact with conductive materials.
Innovation Solution
The capacitive sensor design incorporates a sensor sheet with a central electrode layer and two outer electrode layers, where the total capacitance is measured from two detection portions, with the outer electrode layers being electrically connected to reduce environmental noise interference and enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is provided to prevent conduction between electrode layer and external member, then flexibility of the sensor sheet is maintained, but the thickness of the protective layer must be made thin which fails to sufficiently suppress capacitance fluctuation caused by electromagnetic noise
Solution Approach 1:
A protective layer made of elastomer material is introduced as an intermediary between the electrode layers and the external environment. This protective layer serves as a mediator that provides both mechanical protection to maintain flexibility and electrical isolation to suppress electromagnetic noise interference, resolving the contradiction between thin-layer flexibility and noise suppression capability
Solution Approach 2:
The protective layer is constructed from composite materials, specifically elastomer compositions that combine mechanical flexibility with electrical insulation properties. This composite material approach allows the protective layer to simultaneously provide flexibility for conformal deformation and sufficient thickness for electromagnetic noise suppression
2Measurement precision
If electrode layers are exposed to detect deformation, then measurement sensitivity is improved, but capacitance fluctuation due to contact with conductors and electromagnetic noise increases
Solution Approach 1:
The protective layer acts as an intermediary that allows the electrode layers to remain functionally exposed for deformation detection while providing necessary isolation from environmental interference. The elastomer material transmits mechanical deformation to the electrode layers while blocking electromagnetic noise and preventing conductor contact
Solution Approach 2:
A flexible protective shell or thin film is applied over the electrode layers. This flexible protective covering maintains the electrode layers' ability to detect deformation through conformal contact while providing a barrier against electromagnetic noise and conductor contact that causes capacitance fluctuation
3Adaptability or versatility
If the sensor sheet is made thin to conform to flexible measuring objects, then adaptability is improved, but susceptibility to electromagnetic noise and environmental interference increases
Solution Approach 1:
The sensor sheet is constructed as a thin flexible structure that can conform to the measuring object's surface. This thin flexible design provides high adaptability while the integrated protective layer ensures sufficient electromagnetic noise suppression without compromising conformability
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 effectively minimizes capacitance fluctuations caused by environmental noise, ensuring more accurate and stable measurements even in noisy conditions or when the sensor is in contact with conductive materials.
Implementation Method 1
since the dielectric layer is formed from an elastomer, the dielectric layer is capable of repeated elastic deformation
Implementation Method 2
capacitance in a capacitive sensor is represented by the following Formula (1): C＝ε 0 ε r S/d
Implementation Method 3
since the various electrode layers contain carbon nanotubes, the electrode layers can change their shapes in conformity with the deformation of the dielectric layer
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Provided is a capacitive sensor (1) in which fluctuation in the measured value of capacitance caused by the use environment is small. Disclosed is a capacitive sensor (1) which includes a sensor sheet (2) and a measuring instrument (3), the sensor sheet (2) including a central electrode layer (12A); a first dielectric layer (11A) laminated on the upper surface of the central electrode layer (12A); a second dielectric layer (11B) laminated on the lower surface of the central electrode layer (12A); a first outer electrode layer (12B) formed on the surface of the first dielectric layer (11A) on the opposite side of the central electrode layer (12A) side; and a second outer electrode layer (12C) formed on the surface of the second dielectric layer (11B) on the opposite side of the central electrode layer (12A) side, in which the first dielectric layer (11A) and the second dielectric layer (11B) are formed from elastomers, the part where the central electrode layer (12A) and the first outer electrode layer (12B) face each other is designated as a first detection portion, while the part where the central electrode layer (12A) and the second outer electrode layer (12C) face each other is designated as a second detection portion, the sensor sheet is (2) reversibly deformable, and the capacitances of the first detection portion and the second detection portion change with deformation. The state of deformation of the sensor sheet (2) is measured on the basis of the total capacitance by adding the capacitance of the first detection portion and the capacitance of the second detection portion.