Capacitive Sensor Integration Cycles for Higher-Resolution Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring capacitance values in capacitive touch sensors face challenges due to the small and variable nature of the capacitance changes, which are limited by the resolution of the A/D converter, leading to quantization errors and difficulty in distinguishing between capacitance states.
Innovation Solution
The method involves setting a range of integration cycles, initializing a voltage sum, and incrementally increasing the number of cycles while measuring the voltage with an A/D converter, allowing for the accumulation of voltage values to compensate for quantization errors and improve resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard integration method with fixed number of cycles is used, then the measurement process is simple, but the measurement resolution is limited by A/D converter quantization errors
Solution Approach 1:
The measurement process is segmented into multiple passes, where each pass performs a different number of integration cycles (N, N+1, N+2, etc.). This segmentation allows the system to capture voltage values at different integration stages and combine them to achieve higher resolution than a single fixed-number integration could provide, effectively overcoming the A/D converter's quantization limitation.
Solution Approach 2:
The measurement is performed periodically in multiple passes with incrementally increasing numbers of integration cycles. Each pass is a periodic action that contributes to the final high-resolution measurement by accumulating voltage values that collectively resolve the quantization error through their sum.
2Measurement precision
If the number of integration cycles is increased to improve resolution, then measurement precision improves, but measurement time increases
Solution Approach 1:
Instead of performing a very large number of integration cycles in a single pass (which would be time-consuming), the method performs multiple passes with progressively increasing cycles (N, N+1, N+2). This partial action approach achieves the resolution benefit of many cycles while distributing the time cost across multiple shorter operations that can be optimized and parallelized.
Solution Approach 2:
The first pass performs a baseline number of integration cycles (N) to establish an initial voltage measurement. Subsequent passes add incremental cycles (1, 2, etc.) to refine the measurement. This preliminary action allows the system to quickly establish a baseline and then make finer adjustments, reducing the total time compared to performing all integration cycles from scratch in a single long pass.
3Measurement precision
If multiple measurement passes with different integration cycle numbers are performed, then measurement resolution is enhanced, but the number of operations increases
Solution Approach 1:
The voltage values from multiple measurement passes are merged (summed) to produce the final high-resolution measurement result. By combining the results of passes with different integration cycle counts, the system achieves enhanced resolution without requiring each individual pass to be extremely long, thus maintaining better productivity compared to single-pass methods.
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 measurement resolution and reduces quantization errors, enabling more precise detection of capacitance changes in capacitive touch sensors.
Implementation Method 1
small amounts of charge are transferred in several successive cycles from the sensor element, whose capacitance value is relatively small and variable, to an integrating capacitor with a known, fixed, and significantly larger capacitance value
Implementation Method 2
The resolution of these measurement methods—and thus the limit for distinguishing between two states or capacitance values—is largely determined by the resolution of the analog-to-digital converter (ADC) used. An ADC can only measure voltages in certain discrete steps. These steps are also called quantization intervals.
Data Source
Figure 1a~1b
Figure 2
AI summary
The invention relates to a method for measuring a capacitance value CM of a capacitive sensor element by means of an integration method, wherein a terminal of the sensor element is electrically connected to a first terminal of an integration capacitor having a known capacitance value CI, which is high by comparison with the capacitance value CM of the sensor element, at a common circuit node, and wherein after a number IZ of integration cycles have been carried out, a voltage UCI at the integration capacitor is measured by means of an A/D converter. The method according to the invention comprises the method steps of: a) defining a number N of integration cycles to be carried out at a start value NStart and determining an end value NEnd for the number N of integration cycles to be carried out b) initializing a voltage sum value UGes to the value of zero c) initializing the number IZ of executed integration cycles to the value of zero d) connecting the common circuit node (3) and a second terminal (2'') of the integration capacitor (2) to an earth potential GND e) carrying out the integration method until the number IZ of executed integration cycles has reached the number N of integration cycles to be carried out f) adding the voltage value UCI(N) currently determined by means of the A/D converter, to the voltage sum value UGes g) increasing the number N by a value n, wherein n is greater than or equal to 1 and is less than NDiff = NEnd - NStart , h) repeating the method steps from step e) until the number N exceeds the determined end value NEnd i) evaluating the voltage sum value UGes as the measurement result.