Double-Electrode Capacitive Sensor Parasitic Capacitance Elimination
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Solution Overview
Problem
Existing double-electrode capacitance sensors have limitations in detection sensitivity, particularly in distinguishing between a passenger seated and not seated on a vehicle seat, due to variations in capacitance between electrodes and parasitic capacitance, which affect detection accuracy and frequency usability.
Innovation Solution
A double-electrode capacitive sensor design with an electrode assembly on an insulation substrate, where the first and second electrodes are overlapped and coupled with a ground, using a detection circuit that applies an alternating voltage and includes an oscillation circuit and differential amplifier to improve detection accuracy and prevent oscillation, allowing for increased usable frequency and enhanced detection of capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection sensitivity is increased by using a double-electrode capacitance sensor, then the detection accuracy improves, but the parasitic capacitance between electrodes increases causing oscillation and limiting usable frequency
Solution Approach 1:
The patent extracts and eliminates the parasitic capacitance component by using a differential amplifier circuit that subtracts the capacitance between the two electrodes from the total capacitance measurement. This separation allows the sensor to maintain high detection sensitivity while removing the harmful oscillation-causing parasitic capacitance, thereby resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The differential amplifier circuit acts as an intermediary between the electrode assembly and the detection output. It processes the raw capacitance signal by eliminating parasitic components, thereby enabling both high detection accuracy and stable frequency operation without direct interference between the electrodes.
2Measurement precision
If the capacitance change detection sensitivity is improved, then the passenger detection accuracy increases, but the circuit becomes more susceptible to oscillation
Solution Approach 1:
The patent converts the harmful parasitic capacitance into a useful differential signal. By measuring the capacitance between both electrodes and using a differential amplifier to subtract the common-mode parasitic capacitance, the circuit transforms what was previously a source of oscillation into a reference signal that enhances detection accuracy while improving circuit stability.
3Device complexity
If the detection circuit uses a simple single-electrode design, then the device complexity is reduced, but the detection sensitivity is insufficient
Solution Approach 1:
The patent segments the detection function into two separate electrodes working in parallel, each contributing to the overall detection capability. This segmentation allows the system to achieve higher detection sensitivity through differential measurement while maintaining a relatively simple overall structure that can be easily integrated into existing seat systems.
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 improved sensor design enhances detection accuracy for passengers by effectively distinguishing between seated and unseated states, leading to a more reliable passenger detection system and increased safety through better passenger protection in vehicular collisions.
Implementation Method 1
The detection circuit detects a capacitance change between the first electrode and the ground when the detection object approaches the first electrode
Implementation Method 2
a double-electrode capacitive sensor for detecting a detection object made of dielectric material
Implementation Method 3
The oscillation circuit applies the alternating voltage between the ground and the one of the first and second electrodes
Data Source
AI summary
A double-electrode capacitive sensor for detecting a detection object includes: an electrode assembly having first and second electrodes and an insulation substrate; and a detection circuit. The first and second electrodes are disposed on first and second surfaces of the substrate, respectively. The detection circuit applies an alternating voltage between a ground and the first electrode, and detects an electric potential of the second electrode, or controls the electric potential of the second electrode to follow the alternating voltage. The detection circuit detects a capacitance change between the first electrode and the ground when the detection object approaches the first electrode for determining whether the detection object approaches the first electrode. A periphery of the second electrode is substantially opposite to a periphery of the first electrode.