Capacitive Sensor Excitation Schemes for Rotational Input Stability
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Solution Overview
Problem
Rotatable input objects with electrodes that alter capacitance pose challenges in maintaining stable electrical potential, leading to variations in capacitance readings, which complicates accurate detection of rotational information in capacitive sensing devices.
Innovation Solution
The implementation of a processing system that drives sensor electrodes with both sensing and reference signals, and electrically floats adjacent electrodes to mitigate external voltage effects, allowing for precise determination of rotational information by stabilizing the electrical potential of the rotatable input object's electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotatable input objects with electrodes are used to provide rotational input, then the functionality and versatility of the input device is improved, but the electrical potential stability deteriorates leading to variations in capacitance readings
Solution Approach 1:
The patent introduces a reference electrode as an intermediary element that provides a stable electrical potential reference. This reference electrode acts as a mediator between the rotatable input object's electrodes and the sensing circuitry, allowing the system to maintain stable capacitance measurements despite the dynamic rotation of the input object. The reference electrode compensates for potential drift and external voltage effects by providing a constant potential baseline.
Solution Approach 2:
The patent employs different excitation schemes that change the electrical parameters applied to sensor electrodes based on their spatial position and function. By dynamically adjusting the drive signals - using reference signals for certain electrodes and sensing signals for others - the system adapts to the rotational position and maintains stable capacitance readings throughout the rotation cycle.
2Measurement precision
If sensor electrodes are driven with sensing signals to detect capacitance changes, then the measurement precision of rotational information is improved, but the electrical potential stability deteriorates due to external voltage effects
Solution Approach 1:
The reference electrode serves as an intermediary that isolates the sensing electrodes from external voltage effects. By providing a stable reference potential, it mediates the interaction between the sensing signals and the external environment, preventing external voltage fluctuations from directly affecting the capacitance measurements while still allowing precise rotational detection.
Solution Approach 2:
The system uses the reference electrode to provide feedback about the electrical potential state. The reference signal allows the sensing circuitry to compensate for external voltage effects by comparing the actual electrode potential against the stable reference, thereby maintaining measurement precision despite potential stability issues caused by external factors.
3Productivity
If multiple sensor electrodes are driven simultaneously with sensing signals, then the productivity and response time of the input device is improved, but the device complexity increases due to the need for stable potential maintenance
Solution Approach 1:
The reference electrode acts as a shared intermediary resource that simplifies the potential control complexity. Instead of requiring complex individual potential control for each sensor electrode, the system uses the reference electrode as a common stable potential source that all sensing electrodes can reference simultaneously, enabling parallel operation without proportionally increasing control complexity.
Solution Approach 2:
The reference electrode serves multiple functions simultaneously: it provides a stable potential reference for all sensing electrodes, compensates for external voltage effects across the entire sensor array, and enables synchronized operation of multiple electrodes. This multi-functionality allows simultaneous driving of multiple sensor electrodes without linearly increasing the complexity of potential maintenance.
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
This approach enhances the accuracy of rotational information detection by minimizing variations in electrical potential, thereby improving the reliability of capacitive sensing in devices with rotatable input objects.
Implementation Method 1
The third sensor electrode is capacitively coupled with an electrode of an input object
Data Source
AI summary
A system and method for capacitive sensing comprises driving a first sensor electrode of a plurality of sensor electrodes with a first sensing signal to acquire a first resulting signal with the first sensor electrode during a period and driving a second sensor electrode of the plurality of sensor electrodes with the first sensing signal to acquire a second resulting signal with the second sensor electrode during the period. Further, a third sensor electrode of the plurality of sensor electrodes is driven with a reference signal during the period. Rotational information for an input object is determined at least partially based on the first resulting signal and the second resulting signal.