Capacitance Sensor Noise Reduction via Dual-Frequency Selection
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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 reduction by subtracting the noise value from the capacitance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance sensor uses a sense electrode to detect user input, then the sensor can detect the location of input, but the sense electrode is susceptible to electrical noise which decreases detection accuracy
Solution Approach 1:
A separate noise sense electrode is introduced as an intermediary element to measure electrical noise independently from the main sense electrode. This noise measurement is then used to compensate for noise interference in the capacitance measurement, thereby improving detection accuracy without requiring changes to the primary sensing mechanism.
Solution Approach 2:
The sensing function is segmented into two separate electrodes: a main sense electrode for detecting user input and a separate noise sense electrode for measuring electrical noise. This segmentation allows independent measurement and compensation of noise, enabling the system to maintain high detection accuracy even in noisy environments.
2Measurement precision
If separate noise sense electrodes are added to measure and compensate for noise, then noise interference is reduced, but the device complexity increases
Solution Approach 1:
The noise sense electrode serves multiple functions: it measures electrical noise in the environment, provides reference data for compensation algorithms, and can be integrated into existing sensor arrays without requiring completely separate hardware systems. This multi-functionality reduces the overall complexity increase compared to dedicated noise cancellation systems.
Solution Approach 2:
The noise sensing capability is merged with the existing capacitance sensor structure by using the same electrode array for both capacitance measurement and noise measurement. This integration approach minimizes additional hardware requirements and simplifies the overall system architecture while still achieving noise reduction.
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 user input detection by reducing noise interference, improving the precision of 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
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.