Guard-Ring Capacitive Proximity Sensing With DC Feedback
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Solution Overview
Problem
Capacitive sensors lack sufficient sensitivity due to uncontrolled stray capacitance and leakage currents, and their power requirements are high due to the inclusion of AC sources and oscillators, limiting their effectiveness in low-power applications.
Innovation Solution
A non-contact proximity sensor design that decouples a capacitive sensing electrode from its environment using a guard ring, driven by a direct current (DC) power source, with the guard ring voltage controlled by feedback from the capacitive sensor, reducing parasitic capacitance and leakage currents, and allowing for low-power operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC sources and oscillators are used in capacitive sensors, then sensitivity is improved, but power consumption increases
Solution Approach 1:
The patent changes the operating parameter from AC to DC voltage, eliminating the need for oscillators while maintaining sensing capability through direct voltage application to the capacitive sensor and guard ring structure
Solution Approach 2:
The patent removes the AC source and oscillator components from the sensor system, using only DC voltage sources to drive both the capacitive sensor and guard ring, thereby eliminating the power consumption associated with oscillating circuits
2Measurement precision
If guard ring is added to control stray capacitance, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The guard ring acts as an intermediary element driven by DC voltage to control stray capacitance and leakage currents, improving sensitivity without requiring complex AC circuitry or oscillators
Solution Approach 2:
The patent combines the guard ring function with DC voltage driving, merging the stray capacitance control function with the power supply system to reduce overall device complexity while maintaining high sensitivity
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 enhances sensitivity and reduces power consumption, enabling the detection of object movement with improved accuracy and efficiency, while maintaining low power requirements.
Implementation Method 1
capacitive proximity sensors generally known. Systems using capacitive proximity sensors typically measure the capacitance (or change in capacitance) of a sensing electrode as an object being sensed moves in relation to the electrode
Implementation Method 2
the non-contact proximity sensor includes a capacitive sensor decoupled from a surrounding environment by a guard ring. Both the capacitive sensor and the guard ring are driven by a direct current (DC) power source, with the guard ring driven based on feedback from the voltage applied to the capacitive sensor
Data Source
AI summary
A low-power non-contact proximity sensor with improved sensitivity. In particular, the non-contact proximity sensor includes a capacitive sensor decoupled from a surrounding environment by a guard ring. Both the capacitive sensor and the guard ring are driven by a direct current (DC) power source, with the guard ring driven based on feedback from the voltage applied to the capacitive sensor.