Segmented Driven Shield for Capacitance Sensor Noise Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Self-capacitance sensors face challenges in distinguishing parasitic capacitance from desired capacitance, especially as sensor size increases, leading to electrical noise that distorts sensing signals and reduces proximity sensitivity.
Innovation Solution
The shield electrode is divided into multiple portions, with some driven and others grounded, allowing for increased drive voltage on the driven portions without increasing parasitic capacitance, thereby enhancing proximity sensitivity and shielding from electrical noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive voltage on the shield is increased to increase the projected electric field and proximity sensitivity, then the proximity sensitivity is improved, but the parasitic capacitance increases at the same rate
Solution Approach 1:
The shield electrode is divided into multiple portions (first shield portion, second shield portion, third shield portion) with different voltage assignments. The first shield portion is driven with a first voltage, the second shield portion with a second voltage, and the third shield portion is grounded. This segmentation allows the driven portions to generate the necessary electric field for proximity sensitivity while the grounded portion provides a reference potential that prevents the overall parasitic capacitance from increasing proportionally with the drive voltage.
2Area of stationary object
If the sensor size is increased to maximize the driven conducting plate area, then the capacitance sensing capability is improved, but the electrical noise increases distorting the sensing signal
Solution Approach 1:
The shield electrode is segmented into multiple portions with different voltage assignments. The driven portions generate electric field to enhance sensing capability while the grounded portion provides noise shielding. This allows large sensor areas to maintain low noise levels by distributing the voltage potential across multiple shield portions rather than having a single high-voltage shield that would generate excessive parasitic effects and noise.
3Measurement precision
If the gain is increased to amplify the capacitance signal, then the measurement sensitivity is improved, but the effect of parasitic capacitance is increased at the same rate
Solution Approach 1:
By dividing the shield into multiple portions with different voltages, the patent creates a more controlled capacitive environment. The grounded third shield portion provides a stable reference that reduces the impact of parasitic capacitance on the measurement, allowing higher gain to be applied without proportionally amplifying the parasitic capacitance effect.
Solution Approach 2:
The multi-portion shield structure acts as an intermediary between the driven conducting plate and the external environment. By introducing intermediate shield portions with controlled voltages between the high-voltage drive electrode and ground, the patent mediates the parasitic capacitance effects, allowing for higher measurement gain without proportional increases in parasitic interference.
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 configuration effectively reduces parasitic capacitance while maintaining or improving proximity sensitivity and electric field projection, allowing for more precise capacitance measurements.
Implementation Method 1
An increase in electric field would increase the proximity sensitivity but increasing the drive voltage on the shield without any other changes also increases the parasitic capacitance
Implementation Method 2
providing a dielectric base layer with first and second surface, providing a capacitance sense electrode adjacent to the first surface of the dielectric base layer
Data Source
AI summary
Improved driven shield electrodes used with capacitance sensors are described in this application. Typical capacitance sensors suffer from parasitic capacitance that can make proximity sensing difficult. The driven shield described herein is divided into multiple portions and an increased drive voltage is applied to at least one of these portions. This increase voltage enhances the electric field of the capacitance sensor and increases the proximity sensitivity. Other embodiments are described.