Capacitive Sensor Signal Ratio Position Determination
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Solution Overview
Problem
Capacitance sensing systems face errors in determining the position of input objects due to variations in system gain levels and common mode noise, leading to inaccurate position calculations.
Innovation Solution
The use of signal ratios, such as the ratio of differences or the binary logarithm of signal ratios, to uniquely represent the position of input objects, which are modeled through mathematical equations or stored in data structures, effectively cancels out noise and system gain variations, reducing the need for further error correction processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance sensing systems use sensor signals to determine position of input objects, then position determination is achieved, but measurement precision deteriorates due to system gain level variations and common mode noise
Solution Approach 1:
The patent introduces signal ratios as an intermediary quantity that mediates between the raw sensor signals and the final position determination. By computing ratios of sensor signals from different sensor elements, the system creates a new measurement quantity that is invariant to system gain level variations and common mode noise, thereby resolving the contradiction between achieving position determination and eliminating harmful factors
Solution Approach 2:
The patent transforms the measurement parameter from raw sensor signal values to signal ratios. This parameter transformation changes the mathematical properties of the measurement, making it insensitive to multiplicative gain variations and additive common mode noise while preserving the positional information, thus improving measurement precision without being affected by the harmful factors
2Reliability
If algorithm-based methods are used to calculate position from sensor signals, then position calculation is achieved, but reliability deteriorates due to problematic jumps in calculated positions
Solution Approach 1:
The patent uses signal ratios as an intermediary that provides a more stable basis for position calculation compared to direct algorithm-based methods. The ratio formulation inherently reduces sensitivity to noise and gain variations, leading to smoother and more reliable position calculations without the problematic jumps that occur with conventional algorithms
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 improves the accuracy and consistency of position determination by mitigating errors caused by noise and system gain variations, while avoiding problematic jumps in calculated positions, compared to algorithm-based methods.
Implementation Method 1
Capacitive sensing typically involves measuring, through sensor signals, a change in capacitance associated with the capacitive sensor elements to determine a presence of a conductive object relative to the capacitive sensor elements.
Data Source
AI summary
A method and apparatus receive a plurality of signal values, the plurality of signal values responsive to an input object. The method and apparatus calculate at least one signal ratio value using the plurality of signal values and determine a position of the input object using the at least one signal ratio value.