Stacked Capacitive Proximity Sensor for Permittivity Discrimination
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Solution Overview
Problem
Conventional proximity sensors struggle to discriminate between objects of different permittivity, leading to false detections and inability to accurately determine proximity based on size and material properties.
Innovation Solution
A capacitive proximity sensor with a stacked electrode structure and shield control unit that measures capacitance in different modes to distinguish between conductive and dielectric bodies, using a readout circuit to determine permittivity and distance, and transmit data via a digital bus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive proximity sensors are used, then the sensor structure is simple and easy to integrate, but the sensor cannot discriminate between objects of different permittivity leading to false detections
Solution Approach 1:
The sensor electrode is divided into multiple segments or zones, each capable of detecting capacitance changes independently. This segmentation allows the system to analyze spatial distribution of dielectric objects and distinguish between different permittivity values, thereby improving measurement precision without requiring a completely new sensor architecture
Solution Approach 2:
The patent introduces a temporal dimension by implementing periodic switching between different electrode configurations or measurement modes. This allows the system to capture capacitance variations over time and differentiate objects based on their permittivity characteristics, enhancing discrimination accuracy while maintaining relatively simple hardware
2Measurement precision
If optical detection techniques are used for proximity sensing, then discrimination between different objects is possible, but power consumption increases and integration becomes more complex and costly
Solution Approach 1:
The patent replaces optical detection mechanisms with electrical field-based capacitive sensing. By using electrostatic fields instead of light, the system achieves object discrimination through permittivity measurement while consuming significantly less power and avoiding the complexity of optical components, thus resolving the contradiction between measurement precision and energy consumption
3Measurement precision
If conventional proximity sensors are used in wearable devices, then space is limited, but accurate discrimination between body parts and inanimate objects is required
Solution Approach 1:
The patent combines multiple sensing functions into a single integrated capacitive sensor structure. By merging proximity detection, object discrimination, and spatial localization capabilities into one compact sensor, the system achieves high measurement precision while minimizing the volume occupied in wearable devices
Solution Approach 2:
The sensor is designed to perform multiple functions simultaneously: detecting proximity, discriminating object types based on permittivity, and determining spatial position. This multi-functionality allows accurate object discrimination within a compact form factor suitable for wearable applications
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 sensor effectively discriminates between objects of different permittivity, reducing false detections and providing accurate proximity information with minimal space requirements, suitable for integration in portable devices.
Implementation Method 1
the first electrode has a plurality of openings that allow a partial capacitive coupling between the internal electrode and conductive and/or dielectric bodies in the detection region
Implementation Method 2
the first electrode screens partially the internal electrode
Implementation Method 3
a shield control unit configured to generate a shield potential following that of an electrode whose capacitance is measured
Data Source
AI summary
A capacitive proximity sensor with a stacked electrode structure where an inner electrode is partially screened by an upper one. The self-capacitances of selected electrodes is measured while other electrodes are held to ground or to a shield potential. In this manner, the proximity sensor estimates a value of the dielectric permittivity of the approaching body.