Capacitance Sensor Noise Measurement Using Shielded Sense Electrodes
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Solution Overview
Problem
Capacitance sensors in devices like laptops and touchscreen computers are susceptible to electrical noise, which affects their ability to accurately detect user input.
Innovation Solution
A capacitance module with a set of electrodes and separate noise sense electrodes, shielded from the capacitance electrodes, takes simultaneous noise measurements at different frequencies to determine a capacitance measurement frequency, allowing for noise subtraction and improved input detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance sensor uses sense electrodes to detect user input, then the ability to detect input location is enabled, but electrical noise on the sense electrodes decreases measurement accuracy and precision
Solution Approach 1:
The patent divides the sensing function into separate components: capacitance sense electrodes for measuring capacitance values and separate noise sense electrodes for measuring electrical noise. This segmentation allows independent optimization of each function and enables noise subtraction from the capacitance measurement to improve accuracy.
Solution Approach 2:
The patent introduces noise sense electrodes as intermediary elements that measure the electrical noise environment separately. These noise measurements serve as a reference that can be subtracted from the capacitance sense electrode measurements, acting as a mediator to eliminate the harmful noise effect.
2Measurement precision
If separate noise sense electrodes are added to measure and subtract noise, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The patent segments the sensing system into distinct capacitance sensing elements and noise sensing elements, allowing the noise measurement function to be added as a separate, modular component rather than complicating the existing capacitance sensing structure.
Solution Approach 2:
The noise sense electrodes serve multiple purposes: they measure electrical noise for subtraction from capacitance measurements, and can potentially be used for other sensing functions. This multi-functionality justifies the added complexity by providing additional capabilities within the same sensor structure.
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 reduces noise interference, enhancing the accuracy and precision of user input detection by isolating noise measurements from capacitance measurements.
Implementation Method 1
a capacitance sensor may be used to detect user input. A capacitance sensor generally detects input by applying a voltage to a transmit electrode in the capacitance sensor and measuring the change in the electric field on a sense electrode in the capacitance sensor
Implementation Method 2
A capacitance module with a set of electrodes and separate noise sense electrodes, shielded from the capacitance electrodes
Data Source
AI summary
Using a capacitance sensor may include taking a first noise measurement by imposing a first signal on a capacitance sensor, the first signal having a first frequency; taking a second noise measurement by imposing a second signal on the capacitance sensor, the second signal having a second frequency different than the first frequency; determining the measurement with the lower amount of noise between the first noise measurement and the second noise measurement; and taking a capacitance measurement by imposing a third signal on the capacitance sensor, the third signal having either the first frequency or the second frequency based, at least in part, on the frequency of the measurement with the lower amount of noise.