Capacitive Fluid Sensor Electrode Layout to Reduce Stray Capacitance
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Solution Overview
Problem
Existing fluid-property detection devices suffer from reduced detection accuracy due to increased stray capacitance caused by filling molding resin between electrodes, which interferes with the electrostatic capacitance measurement.
Innovation Solution
The device incorporates insulating spacers with recessed portions and through holes to create hollow spaces between electrodes, reducing stray capacitance and maintaining a consistent distance between the inner and outer electrodes, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molding resin is filled in the space between electrodes without forming a gap, then electrode insulation is improved, but stray capacitance increases and detection accuracy deteriorates
Solution Approach 1:
The insulating member is designed with different thicknesses in different regions: a first thickness in the detection region (where electrodes are exposed to fluid) and a second thickness in the non-detection region. This local differentiation allows the non-detection region to have reduced insulating material thickness, minimizing stray capacitance while the detection region maintains adequate insulation. The insulating member thus has non-uniform local properties optimized for different functional requirements.
2Measurement precision
If electrodes are positioned close to each other, then detection sensitivity is improved, but risk of electrical breakdown increases
Solution Approach 1:
The insulating member provides electric field confinement primarily in the detection region where electrodes are positioned close together for high sensitivity. The insulating material is concentrated in this region rather than uniformly distributed, allowing close electrode spacing for detection purposes while maintaining electrical insulation where needed. The non-detection region has reduced insulating material, accepting lower insulation requirements since breakdown risk is minimal there.
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 configuration enhances detection accuracy by minimizing stray capacitance, ensuring precise electrostatic capacitance measurements and maintaining device reliability.
Implementation Method 1
an insulating member configured to insulate between the first electrode and the second electrode
Implementation Method 2
detects electrostatic capacitance between a tip end portion of the outer electrode and a tip end portion of the inner electrode
Data Source
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AI summary
A fluid-property detection device (100) includes a first electrode (30), a second electrode (20) provided so as to face the first electrode (30), and an insulating member (50) provided between the first electrode (30) and the second electrode (20), the insulating member (50) being configured to insulate between the first electrode (30) and the second electrode (20). The insulating member (50) is provided with a reduced-thickness portion (154) for forming a hollow portion (153) between the first electrode (30) and the second electrode (20) in a region (A2) in which the first electrode (30) and the second electrode (20) are not exposed to the detection target fluid.