Capacitive Sensor Ground Mass Correction Mechanism
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Solution Overview
Problem
Capacitive input devices often face issues with low ground mass, particularly when used on non-conductive insulated surfaces without sufficient grounding, leading to inaccurate capacitive measurements.
Innovation Solution
The system acquires capacitive measurements in two different states, one with improved grounding, allowing for the determination of positional information by calculating a low ground mass coefficient to correct for measurement distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive measurements are acquired on non-conductive insulated surfaces, then the input device can be used in various environments, but the ground mass is insufficient leading to inaccurate measurements
Solution Approach 1:
The system performs preliminary capacitive measurements in a first state with initial grounding conditions, then transitions to a second state with improved grounding to acquire additional measurements. These preliminary measurements are used to establish a baseline that is later corrected using the improved grounding state, allowing the system to pre-compensate for low ground mass effects before final position determination.
Solution Approach 2:
The system changes the grounding parameter by transitioning between at least two different states with different grounding conditions. By varying the grounding state and acquiring capacitive measurements in each state, the system can calculate correction factors that account for the low ground mass condition, thereby maintaining measurement precision across different environmental conditions.
2Ease of operation
If the input device is used without sufficient grounding, then it can operate on insulated surfaces, but the capacitive measurements become distorted
Solution Approach 1:
The system uses feedback by comparing capacitive measurements taken in different grounding states. The measurements from the first state (with less optimal grounding) are compared against measurements from the second state (with improved grounding), and correction factors are calculated and applied to compensate for the grounding deficiencies, ensuring reliable position detection even when operated on insulated surfaces.
3Measurement precision
If grounding is improved for accurate measurements, then measurement precision increases, but the device complexity increases due to multiple states
Solution Approach 1:
The system implements dynamic state transitions where the grounding configuration can change between at least two states. The sensor module dynamically switches between these grounding states during operation, acquiring capacitive measurements in each state. This dynamic approach allows the system to achieve high measurement precision through multiple measurement conditions without requiring permanently complex hardware, as the state changes are controlled through software or simple switching mechanisms.
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 effectively corrects for low ground mass conditions, enabling accurate determination of positional information and improving the usability of capacitive sensing in various environments.
Implementation Method 1
sensor electrodes configured to sense input objects in a sensing region of the input device... acquire first capacitive measurements when the input device is in a first state, acquire second capacitive measurements when the input device is in a second state
Data Source
AI summary
A processing system for an input device includes a sensor module coupled to sensor electrodes. The sensor module includes sensor circuitry and configured to acquire first capacitive measurements when the input device is in a first state, and acquire second capacitive measurements when the input device is in a second state. The second state has an increased ground as compared to the first state. The processing system further includes a determination module configured to determine positional information for an input object based on the first capacitive measurements and the second capacitive measurements.