Capacitive Touch Sensor Calibration Using Offset Comparison
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Solution Overview
Problem
Electrostatic capacity type touch sensors require frequent and time-consuming calibration due to environmental sensitivity, and incorrect calibration occurs when the operator's finger touches the touch pad during the process.
Innovation Solution
An electrostatic capacity type touch sensor with a sensor circuit, calibration register, and control circuit that adjusts offset values using stored calibration data to minimize calibration time and prevent finger contact errors, by comparing first and third output values to determine offset adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed frequently to compensate for environmental changes, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The system performs preliminary actions by storing multiple calibration data sets in advance and selecting appropriate calibration data based on environmental conditions. The control circuit determines which calibration data to use by comparing current environmental parameters with stored calibration conditions, thereby avoiding time-consuming real-time calibration while maintaining accuracy.
Solution Approach 2:
The invention changes the parameter of calibration frequency from continuous to conditional. Instead of performing calibration whenever needed, the system changes calibration parameters (selecting from pre-stored calibration data) based on environmental condition changes, reducing time loss while maintaining measurement precision through intelligent parameter selection.
2Ease of operation
If calibration is performed without preventing finger contact, then ease of operation is improved, but measurement precision deteriorates due to incorrect calibration
Solution Approach 1:
The control circuit incorporates feedback mechanisms to detect whether the operator's finger is contacting the touch pad during calibration. Based on this feedback, the system determines whether to proceed with calibration or cancel it, preventing incorrect calibration while maintaining ease of operation through automatic detection and user-friendly interaction.
Solution Approach 2:
The control circuit acts as an intermediary between the calibration process and the operator's finger contact. It monitors the touch pad state during calibration and mediates the calibration process by preventing calibration when finger contact is detected, thereby ensuring measurement precision without complicating the user interaction.
3Loss of time
If calibration is performed only when environment changes significantly, then loss of time is reduced, but measurement precision deteriorates due to missed environmental changes
Solution Approach 1:
The system performs preliminary storage of multiple calibration data sets corresponding to different environmental conditions. When calibration is needed, the control circuit quickly selects the appropriate pre-stored calibration data based on current environmental parameters, avoiding time-consuming real-time calibration while ensuring accuracy through pre-prepared environmental-specific calibration data.
Solution Approach 2:
The invention changes the calibration approach from reactive (waiting for significant environmental changes) to proactive (pre-storing calibration data for various conditions). The system monitors environmental parameters and selects appropriate calibration data in advance, reducing time loss while maintaining precision by having ready-to-use calibration parameters for different environmental scenarios.
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
The solution allows for rapid calibration of the touch sensor without operator contact, effectively reducing calibration time and ensuring accurate adjustments to environmental changes, thereby improving detection accuracy and efficiency.
Implementation Method 1
detecting a change in a capacitance of a capacitor associated with a touch pad induced by touching or approaching the touch pad with a finger of an operator or a pen tip
Implementation Method 2
the output value of the electrostatic capacity type touch sensor varies sensitively to its environment (temperature, humidity, electric field from its surrounding environment or the like)
Data Source
AI summary
This invention offers an electrostatic capacity type touch sensor that can be calibrated in a short period of time at a moment when a finger of operator or the like does not touch a touch pad. An absolute value of a difference (AD0−AD2) between a first output voltage AD0 and a third output voltage AD2 is compared with a first threshold value Vtr1 in step S10. When the difference (AD0−AD2) between the output voltages is smaller than the first threshold value Vtr1, it is judged that the finger of operator or the like does not touch the touch pad, and it is judged which of an offset in a second output voltage AD1 and an offset in the third output voltage AD2 is smaller than the other. When the offset in the second output voltage AD1 is smaller than the offset in the third output voltage AD2, the modification to the second calibration data X1 is permitted.