Capacitive Sensing System for Absolute Profile Determination
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Solution Overview
Problem
Conventional capacitance sensing technologies face challenges in accurately measuring absolute capacitance due to parasitic background capacitance being orders of magnitude larger than the capacitance caused by input objects, requiring high charges and leading to inaccurate measurements and potential saturation of sensing circuitry.
Innovation Solution
The implementation of a processing system that performs combined capacitive sensing by simultaneously measuring absolute and transcapacitance signals using a sensor electrode pattern, allowing the reconstruction of absolute capacitance signals from combination signals, thereby reducing the need for high charges and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitance sensing is used to measure absolute capacitance, then measurement capability is provided, but parasitic background capacitance causes measurement inaccuracy and potential circuit saturation
Solution Approach 1:
The patent introduces transcapacitance sensing as an intermediary measurement approach. Instead of directly measuring absolute capacitance which is affected by large parasitic background capacitance, the system measures transcapacitance between sensor electrodes and input objects, which provides a indirect but more accurate measurement path that avoids the saturation problem while still enabling absolute capacitance reconstruction
Solution Approach 2:
The patent changes the measurement parameter from direct absolute capacitance to transcapacitance. By measuring the change in capacitance between sensor electrodes and input objects (transcapacitance) rather than the absolute capacitance value directly, the system transforms the measurement into a form that is less susceptible to parasitic background capacitance effects and enables accurate reconstruction of absolute capacitance signals
2Reliability
If high charges are used to overcome parasitic background capacitance, then measurement signal strength is improved, but circuit saturation risk increases
Solution Approach 1:
The patent changes the measurement approach from direct absolute capacitance measurement requiring high charges to transcapacitance measurement. This parameter change allows the system to achieve reliable measurement signals without needing to apply high charges that would cause circuit saturation, as transcapacitance sensing inherently provides better signal-to-noise ratio at lower charge levels
3Measurement precision
If combined capacitive sensing is implemented, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges absolute capacitance sensing and transcapacitance sensing into a unified combined capacitive sensing system. By combining these two measurement approaches, the system achieves accurate reconstruction of absolute capacitance signals while utilizing existing sensor electrode infrastructure, thereby improving measurement precision without proportionally increasing device complexity
Solution Approach 2:
The patent makes the sensor electrodes multi-functional by using them for both absolute capacitance measurement and transcapacitance measurement. This universality allows the same hardware infrastructure to perform multiple measurement functions, achieving high measurement accuracy without requiring separate dedicated components for each measurement type, thus limiting the increase in device complexity
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 enables accurate reconstruction of absolute capacitance signals with lower charges, enhancing measurement accuracy and reducing the risk of circuit saturation, while maintaining the benefits of conventional absolute capacitance sensing.
Implementation Method 1
conventional capacitance sensing technologies face challenges in accurately measuring absolute capacitance
Implementation Method 2
parasitic background capacitance being orders of magnitude larger than the capacitance caused by input objects
Data Source
AI summary
The invention relates to a processing system. The processing system includes a sensor module performing a first measurement to obtain a combination signal using a first sensor electrode and a second sensor electrode. The first electrode is driven using a first modulated signal with a first driving voltage amplitude and simultaneously the second electrode is driven using a second modulated signal with a second driving voltage amplitude greater than the first driving voltage amplitude, while simultaneously first and second resulting signals are received from the first and second electrodes, respectively. The sensor module is further performs a second measurement to obtain a transcapacitance signal using the first and second sensor electrodes. The processing system also includes a determination module that generates the combination signal by combining the first and second resulting signals, and computes an absolute capacitance signal from the combination signal, the transcapacitance signal, and a background capacitance.