Capacitive Sensor Drift Compensation Using Adaptive Reference Sensing
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Solution Overview
Problem
Capacitive sensor devices in portable electronic devices are prone to drift due to environmental influences such as temperature and humidity, leading to faulty proximity signal detection.
Innovation Solution
A capacitive sensor device with a capacitance-measuring circuit and separate reference sense input, adaptively determining correction coefficients based on current and previously measured reference values to correct for environmental drift in real time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive sensor device measures capacitance in changing environmental conditions, then it can detect proximity in real-world usage, but measurement precision deteriorates due to drift from 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 conditions and the main capacitance measurement, allowing the system to subtract drift effects from the primary measurement and thereby maintain precision while operating in changing environments.
Solution Approach 2:
The system implements feedback by continuously monitoring reference capacitance values and using them to dynamically adjust correction coefficients. These corrected coefficients are then applied to compensate drift in real-time measurements, creating a closed-loop system that maintains measurement precision despite environmental variations.
2Device complexity
If capacitive sensor device uses fixed correction coefficients for drift compensation, then device complexity is reduced, but reliability deteriorates because fixed coefficients cannot adapt to varying environmental conditions
Solution Approach 1:
The patent transitions from static fixed correction coefficients to dynamic adaptive correction coefficients that automatically adjust based on current environmental conditions. The system continuously updates correction coefficients using reference measurements, enabling the correction mechanism to adapt to varying temperature and humidity conditions while maintaining reliability.
Solution Approach 2:
The system performs self-calibration by using its own reference sense input to generate correction coefficients without requiring external calibration equipment or manual intervention. This self-service capability allows the device to maintain reliable drift compensation autonomously across different operating 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
Effectively removes environmental drift from capacitance measurements, enhancing the accuracy of proximity detection in capacitive sensors.
Implementation Method 1
measuring circuit (2) configured to measure 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
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.