Capacitive Sensor Shield Electrode and Protection Circuit
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Solution Overview
Problem
Conventional capacitive sensor apparatuses for steering wheels and other applications face issues with floating capacitance interference and damage from static electricity, leading to complex structures and inaccurate detection.
Innovation Solution
A sensor apparatus featuring a capacitive sensor with a shield electrode and a protection circuit, including a Zener diode connected to ground, which applies AC voltage to both the sensor and shield electrodes to prevent floating capacitance interference and static electricity damage, ensuring accurate detection and minimizing structural complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitive sensor apparatus is used without a shield electrode and protection circuit, then the structure is simpler, but the detection accuracy is reduced due to floating capacitance interference and static electricity damage
Solution Approach 1:
A shield electrode is introduced as an intermediary component between the sensor electrode and the environment. This shield electrode is connected to ground through a protection circuit, mediating the interference from floating capacitance and static electricity before they can affect the sensor electrode, thus improving detection accuracy while adding a controlled level of structural complexity
Solution Approach 2:
The protection circuit, including the shield electrode and grounding connection, provides beforehand cushioning against static electricity and floating capacitance interference. By preparing this protective structure in advance, the sensor electrode is protected from potential damage and interference before they can occur, ensuring stable and accurate detection
2Reliability
If AC voltage is applied to both sensor and shield electrodes, then floating capacitance interference and static electricity damage are prevented, but the circuit complexity increases
Solution Approach 1:
AC voltage is applied periodically to both the sensor electrode and shield electrode. This periodic voltage application creates a reference signal that allows the system to distinguish between actual detection targets and interference from floating capacitance or static electricity, improving reliability through a systematic periodic measurement approach
Solution Approach 2:
The shield electrode is maintained at the same potential as the sensor electrode by applying AC voltage to both. This equipotential condition prevents potential differences that would otherwise cause floating capacitance interference and static electricity damage, achieving improved reliability through potential equalization while using a relatively simple voltage application circuit
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 effectively prevents the influence of floating capacitance and static electricity on detection values, enhancing the accuracy and reliability of capacitive sensing while maintaining a compact design.
Implementation Method 1
a shield electrode provided on the base material so as to surround an outer edge of the sensor electrode and configured to capacitively couple with the sensor electrode
Implementation Method 2
a voltage circuit connected to the shield electrode and configured to output an AC voltage having a predetermined phase and a predetermined voltage
Implementation Method 3
a protection circuit including a first end part connected to a connection part between the voltage circuit and the shield electrode and a second end part connected to ground
Data Source
AI summary
A sensor apparatus includes a sensor electrode provided on a base material; a shield electrode provided on the base material so as to surround an outer edge of the sensor electrode and configured to capacitively couple with the sensor electrode; a voltage circuit connected to the shield electrode and configured to output an AC voltage having a predetermined phase and a predetermined voltage; and a protection circuit including a first end part connected to a connection part between the voltage circuit and the shield electrode and a second end part connected to ground.