Guarded Capacitive Sensing With Integrated Electronics
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Solution Overview
Problem
Capacitive technologies struggle to accurately detect objects at a distance and integrate additional electronic functions without degrading sensitivity due to stray capacitances and electromagnetic disturbances, especially in non-planar surfaces and complex geometries, limiting their effectiveness in gestural and tactile interfaces.
Innovation Solution
A capacitive detection device with a guard electrode excited to an alternating electric potential identical to the measurement electrodes, combined with floating bridge electronics that integrate additional functions referenced to the guard potential, reducing stray capacitances and allowing for enhanced sensitivity and range by treating these functions as part of the guard, thus minimizing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive sensors are used for proximity detection, then sensitivity can be improved, but stray capacitances and electromagnetic disturbances degrade measurement precision
Solution Approach 1:
The patent introduces a guard electrode as an intermediary element positioned between the measurement electrode and the environment. This guard electrode is driven at the same potential as the measurement electrode, effectively shielding it from stray capacitances and electromagnetic disturbances caused by surrounding objects, cables, and circuitry. The guard acts as a mediator that protects the sensitive measurement from harmful external influences.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively counteracting the harmful effects of stray capacitances before they can affect the measurement. The guard electrode is configured to anticipate and neutralize the electromagnetic interference and capacitive coupling from surrounding objects, cables, and circuit board traces before these disturbances can corrupt the measurement signal.
2Adaptability or versatility
If additional electronic functions are integrated near the capacitive sensor, then device functionality is improved, but electromagnetic interference from these functions degrades detection accuracy
Solution Approach 1:
The patent merges the measurement electrode, guard electrode, and additional electronic functions (such as LEDs, displays, or other components) into a single integrated sensor assembly. The guard electrode encompasses and shields both the measurement electrode and the additional electronic functions, allowing them to coexist in close proximity without the latter interfering with the capacitive measurement. This merging enables functional integration while maintaining measurement integrity.
3Adaptability or versatility
If capacitive technology is used on non-planar surfaces, then adaptability to complex geometries is improved, but stray capacitances from the surface structure increase and reduce sensitivity
Solution Approach 1:
The patent applies local quality by configuring the guard electrode to specifically address the local electromagnetic environment created by non-planar surface structures. The guard is positioned and shaped to follow the contours of the complex geometry, providing localized shielding exactly where the measurement electrode interacts with the object. This allows the sensor to adapt to complex geometries while the guard locally compensates for the stray capacitances introduced by those same geometries.
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
Enables accurate detection of objects up to several centimeters with improved sensitivity and range, while allowing integration of additional electronic functions like lighting and displays without degrading the capacitive measurement, enhancing the performance of gestural and tactile interfaces.
Implementation Method 1
a guard made from an electrically conductive material placed adjacent to said measurement electrode(s), which guard is excited up to an alternating electric potential substantially identical to that of the measurement electrodes
Implementation Method 2
reducing stray capacitances and allowing for enhanced sensitivity and range by treating these functions as part of the guard, thus minimizing interference
Implementation Method 3
first electronic means for exciting the electrode(s) and processing the measurement signals from the capacitive coupling of said electrode(s) with an object placed adjacent thereto
Data Source
AI summary
A capacitive measurement device includes: at least one measurement electrode having an active surface; at least one guard made from an electrically conductive material placed adjacent to the measurement electrode(s), the guard being excited up to an alternating electric potential substantially identical to that of the measurement electrodes; and a first electronic device for exciting the electrode(s) and processing the measurement signals from the capacitive coupling of the electrode(s) to an object placed adjacent thereto, the electronic device being at least partially referenced to the electric potential of the guard. The measurement device further includes apparatus for performing another function, placed adjacent to the active surface, and a second electronic device provided for monitoring the apparatus for performing another function, the second electronic device being at least partially referenced to the electric potential of the guard.