Capacitive Floating-Object Detection Using a Polarization Electrode
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Solution Overview
Problem
Capacitive sensors face reduced sensitivity and detection performance when detecting electrically floating objects that are isolated from their environment and have degraded coupling with the reference potential, such as ground potential.
Innovation Solution
A capacitive device that includes a bias electrode to polarize the object to the ground or reference potential, ensuring precise detection even when the object's coupling with the ground potential is degraded, by using a polarization electrode facing the object and arranged at the same level as or below the guard electrode, which effectively guards the measurement electrode and maintains sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor uses a measuring electrode and guard electrode configuration to detect objects, then detection capability is improved, but sensitivity is degraded when the object is electrically isolated from ground potential
Solution Approach 1:
The patent introduces a polarization electrode as an intermediary element between the measuring electrode and the electrically isolated object. This polarization electrode, connected to ground potential, acts as a mediator to establish an electrical reference for the floating object, enabling the capacitive sensing system to detect objects that are otherwise electrically isolated from ground potential.
Solution Approach 2:
The patent segments the electrode system into three distinct functional components: a measuring electrode for capacitance detection, a guard electrode for electrical shielding, and a polarization electrode for establishing ground reference. This segmentation allows each electrode to perform its specific function independently, resolving the contradiction between detection capability and sensitivity for isolated objects.
2Adaptability or versatility
If the object is electrically isolated from the environment, then object independence is improved, but detection performance is degraded due to potential deviation from ground potential
Solution Approach 1:
The polarization electrode is maintained at ground potential and positioned to face the isolated object, creating an equipotential reference surface. This establishes a known electrical reference that allows the measuring electrode to accurately detect capacitance changes even when the object itself is electrically isolated, thereby maintaining detection performance while preserving object independence.
3Measurement precision
If multiple electrode layers are added to improve detection of isolated objects, then detection accuracy is improved, but device complexity is increased
Solution Approach 1:
The polarization electrode serves multiple functions simultaneously: it establishes ground potential reference for isolated objects, shields the measuring electrode from environmental electrical noise, and creates a controlled electrical field for capacitance measurement. This multi-functionality improves detection accuracy without proportionally increasing device complexity, as a single additional electrode layer provides multiple benefits.
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 device achieves precise detection of objects isolated from their environment with maintained sensitivity and performance, as the bias electrode ensures the object is polarized to the ground potential, enhancing detection accuracy and reducing the number of electrode layers and production complexity.
Implementation Method 1
at least one polarization electrode, disposed opposite the object, and polarized at ground potential so as to electrically polarize, by capacitive coupling, said object located on the side of said detection surface
Implementation Method 2
Each measuring electrode is guarded by a guard electrode, polarized at an alternating potential, called the guard potential, which is identical or substantially identical to the alternating potential of the measuring electrode
Data Source
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AI summary
The present invention relates to a device (100) for detecting an object (102) in relation to a detection surface (104), comprising: - a measuring electrode (106); and - at least one guard electrode (108), with the same alternating potential as the measuring electrode (106); and - at least one module (114) for measuring a first signal in relation to the capacitance (Ceo), referred to as the electrode-object capacitance, formed between said measuring electrode (106) and said object (102); characterised in that it further comprises at least one electrode (116), referred to as the polarisation electrode, arranged facing said object (104) and with its potential grounded (M) so as to polarise said object (102) through capacitive coupling.