Capacitive Drift Compensation for Reliable Proximity Sensing
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Solution Overview
Problem
Capacitive sensor devices in portable electronic devices face challenges due to environmental influences like temperature and humidity changes, which cause capacitance drift, leading to faulty proximity signal detection.
Innovation Solution
A capacitive sensor device with a capacitance-measuring circuit and separate reference sense input, capable of adaptively determining correction coefficients based on current and previously measured reference values to correct main capacitance values in real-time, effectively mitigating environmental drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive sensor device measures capacitance in changing environmental conditions, then it can detect proximity in real-world usage, but the capacitance measurements drift due to temperature and humidity changes
Solution Approach 1:
The patent introduces a reference sense input as an intermediary element that measures only environmental drift effects. This reference measurement acts as a mediator between the environmental influences and the main capacitance measurement, allowing the system to separate and compensate for drift effects from actual proximity changes.
Solution Approach 2:
The system implements feedback by continuously monitoring reference capacitance values and using them to adjust correction coefficients. The measured reference values feed back into the correction algorithm, which adaptively updates the correction coefficients to compensate for ongoing environmental drift, thereby maintaining measurement accuracy.
2Measurement precision
If the system uses fixed correction coefficients for drift compensation, then the device complexity is reduced, but the compensation accuracy decreases under varying environmental conditions
Solution Approach 1:
The patent transitions from static fixed correction coefficients to dynamic adaptive correction coefficients. The system continuously adjusts the correction coefficients based on real-time reference measurements, allowing the compensation mechanism to adapt to changing environmental conditions while maintaining a relatively simple implementation through automated adaptation.
3Measurement precision
If the system continuously adapts correction coefficients based on reference values, then drift compensation accuracy is improved, but the processing complexity and energy consumption increase
Solution Approach 1:
The system changes the parameter of correction coefficients from fixed to variable based on reference capacitance measurements. By monitoring changes in reference values and only updating correction coefficients when environmental conditions change, the system achieves accurate drift compensation while minimizing unnecessary processing and energy consumption during stable conditions.
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 solution enables accurate detection of proximity by effectively removing environmental drift from capacitance measurements, improving the reliability of proximity awareness in portable devices.
Implementation Method 1
a capacitive sensor device comprising a capacitance-measuring circuit (2), a main sense input (3), and a reference sense input (4), wherein the capacitive sensor device (1) is configured to measure, using the capacitance-measuring circuit (2), a current main value of capacitance seen by the main sense input (3) and a current reference value of capacitance seen by the reference sense input (4)
Data Source
Figure 1~3
AI summary
The present invention relates to a capacitive sensor device comprising a capacitance-measuring circuit, a main sense input and a reference sense input, wherein the capacitive sensor device is configured to measure, using the capacitance-measuring circuit, a current main value of capacitance seen by the main sense input and a current reference value of capacitance seen by the reference sense input, wherein the capacitive sensor device is configured to at least temporarily store at least one previously measured reference value, and wherein the capacitive sensor device is configured to use 1) the current main value, 2) the current reference value and the at least one previously measured reference value, and 3) at least one current correction coefficient, with the capacitive sensor device being configured to adaptively determine the at least one current correction coefficient based on at least the current reference value and the at least one previously measured reference value, for determining a corrected current main value of capacitance. The present invention further relates to a portable electronic device comprising the capacitive sensor device.