Capacitive Touch Pad Liquid Detection via Multi-Frequency Measurement
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Solution Overview
Problem
Conventional capacitive touch pads fail to effectively recognize the presence of liquid, such as water, on their surface, which interferes with accurate touch information detection.
Innovation Solution
A liquid detection method for capacitive touch pads that involves performing first and second mutual capacitance measurements using different frequencies and sensing times to determine the presence of liquid by analyzing the resulting sensing values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch pad uses single frequency measurement, then the device complexity is low, but the liquid detection accuracy is insufficient
Solution Approach 1:
The measurement process is segmented into multiple independent capacitance measurements at different frequencies. The controller performs first capacitance measurement at first frequency, second capacitance measurement at second frequency, and optionally third capacitance measurement at third frequency. Each measurement provides different information about the touch pad state, and by combining these segmented measurements, the system achieves accurate liquid detection without requiring complex hardware modifications.
2Reliability
If conventional touch pad uses single sensing time, then the productivity is high, but the liquid recognition capability is poor
Solution Approach 1:
The controller performs capacitance measurements periodically at different frequencies in sequence. First capacitance measurement is performed at first frequency, then second capacitance measurement at second frequency, and optionally third capacitance measurement at third frequency. This periodic multi-frequency measurement approach allows the system to gather comprehensive data for reliable liquid recognition while maintaining efficient operation through structured time management.
3Measurement precision
If the controller performs multiple capacitance measurements at different frequencies, then the liquid detection accuracy improves, but the use of energy increases
Solution Approach 1:
The controller performs a sufficient number of capacitance measurements at different frequencies to achieve accurate liquid detection, but not more than necessary. The measurement process includes first capacitance measurement at first frequency, second capacitance measurement at second frequency, and conditionally third capacitance measurement at third frequency only when liquid is detected. This partial or excessive action ensures reliable detection while avoiding unnecessary energy consumption from redundant measurements.
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
Enables accurate detection of liquid on the touch pad by comparing the sensing values obtained from these measurements, improving the device's ability to differentiate between touch inputs and liquid interference.
Implementation Method 1
Capacitive touch pad determines touch information of objects, for example types of the objects and touch positions, according to variations of capacitance
Data Source
AI summary
A liquid detecting method and controller for a capacitive touch pad are disclosed. The method includes performing a first mutual capacitance measurement of sensing points of the capacitive touch pad to obtain multiple first sensing values, and then performing a second mutual capacitance measurement of the sensing points to obtain multiple second sensing values, wherein the first and the second mutual capacitance measurements using different frequency of driving signals or different sensing periods for sensing the multiple sensing points. According to the multiple first sensing values and the second sensing values, whether there is liquid on the capacitive touch pad can be determined.