Liquid Signal Elimination in Projected Capacitive Touch Systems
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Solution Overview
Problem
Projected capacitive touch systems face challenges in distinguishing between liquid signals and object signals, leading to false touch detections due to the conductive nature of liquids like water, saline, and blood, which interfere with electromagnetic field interpretations.
Innovation Solution
The method involves a liquid measurement cycle integrated with object measurement, using driving and sensing electrodes to differentiate between liquid and object signals by applying specific voltages and using analog-to-digital converters to determine signal values, with elimination and start steps to isolate and remove liquid signals, ensuring accurate object signal output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If projected capacitive touch sensing is used to detect touch signals, then touch input recognition is achieved, but liquid signals cause false touch detections
Solution Approach 1:
The patent segments the measurement process into distinct object measurement phases and liquid measurement phases. By separating these measurements in time, the system can identify when liquid is present on the touch surface and exclude liquid signals from object recognition, thereby resolving the contradiction between achieving touch recognition and avoiding false detections from liquid interference.
Solution Approach 2:
The patent performs liquid detection as a preliminary action before final object recognition. By conducting liquid measurements and determining liquid presence before processing object signals, the system can prevent false touch detections while maintaining accurate object recognition when liquid is not present.
2Reliability
If liquid measurement is integrated into object measurement cycle, then liquid signals are eliminated, but measurement time increases
Solution Approach 1:
The patent implements periodic liquid measurements at specific intervals within the object measurement cycle rather than continuous measurement. By performing liquid detection at predetermined periods (e.g., before and after object measurement phases), the system achieves reliable liquid signal elimination while minimizing the time overhead compared to continuous monitoring.
3Measurement precision
If multiple measurements are conducted to distinguish liquid and object signals, then signal accuracy improves, but processing complexity increases
Solution Approach 1:
The patent changes measurement parameters (such as driving voltage levels, measurement timing, and electrode activation patterns) to create distinguishable signal characteristics for liquid versus object interactions. By varying these parameters across different measurement phases, the system achieves high signal differentiation accuracy without requiring overly complex processing algorithms.
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 effectively eliminates liquid signals, preventing false touch detections and ensuring reliable object identification by distinguishing between liquid and object interactions, thus enhancing the accuracy and reliability of touch systems in various environments.
Implementation Method 1
Projected capacitive touch sensing relies on the interpretation of minute changes in electromagnetic fields projected by capacitors embedded in the touch surface caused by the interaction of conductors such as a finger or a touch pen with these fields
Implementation Method 2
the projected capacitive (PCI or PCAP) touch technology integrated in said electronic products
Implementation Method 3
measuring electrical changes of the other sensing electrodes, which are not driven, by an analog-to-digital converter to obtain a liquid signal
Data Source
AI summary
An object identification method of touch system is disclosed. The object identification method includes: repeating an object measurement to obtain a plurality of object signals; conducting a liquid measurement to obtain a liquid signal; determining whether the value of the liquid signal is greater than a first default value or less than a second default value, wherein the first default value is larger than the second default value; proceeding with an elimination step if the value of the liquid signal is greater than the first default value; and, proceeding with a start step if the value of the liquid signal is less than the second default value.