Capacitance Measurement Cycles Varied to Resist EMI Interference
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Solution Overview
Problem
Existing capacitance determination methods for capacitive elements are susceptible to external interference, particularly electromagnetic waves, which reduces the accuracy and reliability of capacitance and touch detection.
Innovation Solution
The method involves varying the duration of successive measurement cycles by dividing them into subsets with different time periods, allowing charge transfer between capacitive elements, and determining capacitance based on the total charge transferred after multiple cycles, thereby reducing the impact of external disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed-frequency charge transfer cycles are used for capacitance measurement, then the measurement process is simple and fast, but the measurement accuracy deteriorates due to susceptibility to external electromagnetic interference
Solution Approach 1:
The patent applies dynamics by making the measurement cycle duration variable rather than fixed. The control unit dynamically adjusts the duration of individual measurement cycles within a measurement series, using different cycle lengths (e.g., short, medium, long cycles) to break the regularity that makes fixed-frequency measurements susceptible to periodic electromagnetic interference. This dynamic variation in timing parameters improves measurement accuracy without requiring additional hardware.
Solution Approach 2:
The patent uses periodic action by implementing repeated measurement cycles with varying durations. Multiple measurement cycles are performed in sequence, each with a different duration, and the results are averaged or combined. This periodic measurement approach with intentional variation in cycle timing allows the system to maintain simplicity while reducing susceptibility to external interference that operates at fixed frequencies.
2Reliability
If multiple measurement cycles with varying durations are performed, then the influence of external disturbances is reduced, but the measurement time increases
Solution Approach 1:
The patent applies partial action by performing a limited number of measurement cycles with varying durations rather than continuously measuring. The system performs enough cycles to achieve the desired reliability (e.g., 3-5 cycles with different durations) and then stops, averaging the results. This avoids excessive measurement time while still obtaining reliable capacitance values by using just sufficient variation to mitigate interference.
3Measurement precision
If charge transfer occurs at predetermined fixed frequency, then the circuit operation is simple and fast, but the accuracy of capacitance determination deteriorates due to interference from external electromagnetic waves with similar frequencies
Solution Approach 1:
The patent applies dynamics by varying the frequency and duration of charge transfer operations across different measurement cycles. Instead of transferring charge at a single fixed frequency, the control unit implements charge transfer at multiple different frequencies by adjusting measurement cycle durations. This dynamic frequency variation allows the system to maintain fast charge transfer rates while avoiding resonance with external electromagnetic interference at specific frequencies.
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 accuracy and reliability of capacitance determination by minimizing the influence of external disturbances, ensuring precise capacitance measurement and improved touch detection.
Implementation Method 1
the capacitive element is charged, and subsequently a charge is transferred from the capacitive element to another capacitive element
Implementation Method 2
a charge is transferred from the capacitive element to another capacitive element
Data Source
Figure 1a~1e
Figure 2~3
AI summary
According to a method for determining the capacitance of a capacitive element (3), during each measurement cycle of a plurality of successive measurement cycles, the capacitive element (3) is charged, and then a charge quantity is transferred to a further capacitive element (5). After the plurality of measurement cycles, a measurement value relating to the total charge quantity transferred is determined, and the capacitance of the capacitive element (3) is determined as a function of the measurement value. A first duration is defined for a first subset of the plurality of measurement cycles, and a different second duration is defined for a second subset of the plurality of measurement cycles.