Electrode Capacitance Timing Circuit With Noise-Averaged Sensing
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Solution Overview
Problem
Capacitance measurements in capacitance measuring circuits are affected by noise, leading to inaccurate results in applications such as touch screens and pressure sensors, due to factors like temperature and humidity changes, and coarse resolution can misinterpret touch events or pressure differences.
Innovation Solution
A capacitance measurement circuit that charges or discharges an electrode between two thresholds, using a counter to measure time and averaging multiple measurements to reduce noise effects, with a controller managing the process to obtain both charging and discharging measurements, thereby attenuating high and low frequency noise for improved accuracy and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single capacitance measurement is performed, then measurement speed is fast, but measurement accuracy is low due to noise
Solution Approach 1:
The patent applies periodic action by performing multiple capacitance measurements in sequence (e.g., 8-16 measurements) and averaging the results. This periodic repeated measurement approach filters out random noise while maintaining acceptable measurement speed through efficient circuit design and parallel processing capabilities.
Solution Approach 2:
The patent implements feedback by using the averaged measurement results to compensate for noise effects. The system continuously performs measurements, averages the results, and uses this feedback to improve measurement accuracy, creating a closed-loop measurement process that reduces the impact of environmental noise and circuit interference.
2Measurement precision
If multiple measurements are averaged, then noise is attenuated and accuracy is improved, but measurement time increases
Solution Approach 1:
The patent merges multiple individual capacitance measurements into a single averaged result. By combining the information from multiple measurements through averaging, the system achieves noise attenuation and improved accuracy while the merged result represents a comprehensive measurement that compensates for individual measurement variations.
Solution Approach 2:
The patent performs preliminary actions by pre-configuring the measurement circuit with optimized parameters, pre-charging capacitors, and preparing the measurement system before actual measurements begin. This preliminary preparation reduces the time required for each measurement cycle, thereby maintaining productivity while allowing multiple measurements to be averaged for improved accuracy.
3Measurement precision
If coarse resolution is used, then measurement range is wide, but touch events and pressure differences are misinterpreted
Solution Approach 1:
The patent applies dynamics by making the measurement system adaptive through averaged measurements. The system dynamically adjusts its effective resolution by performing multiple measurements and averaging, allowing it to achieve fine resolution when needed while maintaining the ability to measure across a wide range of capacitance values. The averaged result provides finer granularity in the measurement scale.
Solution Approach 2:
The patent changes the measurement parameters by averaging multiple measurements, which effectively changes the resolution parameter of the system. This parameter change allows the system to achieve finer capacitance resolution without sacrificing the measurement range, as the averaging process enhances the ability to detect small capacitance variations while the circuit design maintains support for a wide measurement range.
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 provides high-frequency and low-frequency noise attenuation, resulting in fine-resolution, high-accuracy capacitance measurements that effectively reduce noise interference and improve the reliability of touch event detection and pressure sensing.
Implementation Method 1
measuring capacitance of an electrode... a charging/discharging circuit part which charges the electrode or discharges the electrode
Data Source
AI summary
In various examples there is a capacitance measurement circuit for measuring capacitance of an electrode. The circuit comprises a charging/discharging circuit part which charges the electrode or discharges the electrode, and a counter which measures a charging measurement being a time taken by the charging/discharging circuit part to charge the electrode between two charging thresholds, and which measures a discharging measurement being a time taken by the charging/discharging circuit part to discharge the electrode between two discharging thresholds. The circuit has a controller configured to control the charging/discharging circuit part and the counter such that a plurality of discharging measurements are obtained and a plurality of charging measurements are obtained. The circuit has an averaging logic which computes the measured capacitance in relation to an average of the measurements. In this way high frequency and low frequency noise is attenuated and fine resolution, high accuracy capacitance measurements are obtained.