Capacitive Touch Sensing Device Induced Electric Field Detection
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Solution Overview
Problem
Capacitive touch sensing devices face instability and accuracy issues due to the influence of the electric field from the human body and the earth, which are misinterpreted as noise, affecting the measurement of self-capacitance and induced electric fields.
Innovation Solution
A capacitive touch sensing device that detects induced electric fields using a differential amplifier, high impedance resistor, and signal judgment circuit to amplify and filter signals, enabling accurate detection of touch inputs and position measurement, even with gloved users, and expanding to two-dimensional touch detection through a multiplexer and orthogonal conductive wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance increment is used to measure touch contact, then touch detection is achieved, but measurement precision deteriorates due to electric field variations from human body and earth being mistaken as noise
Solution Approach 1:
The patent introduces a differential amplifier as an intermediary component between the touch sensor and the signal judgment circuit. This differential amplifier specifically amplifies the induced electric field signal from the touch sensor while rejecting common-mode signals (including electric field interference from human body and earth), thereby enabling accurate touch detection despite the presence of harmful electric field factors
Solution Approach 2:
The patent replaces the traditional capacitance increment measurement method with an electric field-based detection method using a differential amplifier. Instead of measuring capacitance changes that are susceptible to electric field interference, the system directly detects and amplifies the induced electric field signal, substituting a more robust detection mechanism that is less affected by environmental electric field variations
2Reliability
If self-capacitance measurement is used, then touch sensing is achieved, but stability deteriorates due to electric field differences creating noise in measurement
Solution Approach 1:
The differential amplifier serves as an intermediary that processes the electric field signal from the touch sensor. It selectively amplifies the differential signal component (touch-induced electric field) while rejecting common-mode components (electric field differences from positive and negative poles), thereby improving measurement stability despite the presence of harmful electric field variations
Solution Approach 2:
The patent converts the harmful electric field differences into a beneficial differential signal. By using a differential amplifier, the system leverages the electric field variations (both from touch and from environmental sources) and processes them differentially, allowing the touch-induced signal to be extracted and amplified while the common-mode environmental variations are rejected, thus turning a potentially harmful factor into a useful detection mechanism
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 enhances the accuracy and stability of capacitive touch sensing by effectively distinguishing touch inputs and measuring touch positions, reducing noise interference and enabling reliable operation with gloved users and two-dimensional touch detection.
Implementation Method 1
as the touch sensor receives an induced electric field signal, the differential amplifier amplifies the induced electric field signal
Implementation Method 2
a capacitor, electrically connected to the first input end and the second input end of the differential amplifier for noise filtration
Data Source
AI summary
A capacitive touch sensing device by detecting induced electric field includes a differential amplifier, a resistor and a signal judgment circuit. The differential amplifier is electrically connected to a touch sensor. The resistor is electrically connected to a first input end and a second input end of the differential amplifier. The signal judgment circuit is electrically connected to an output end of the differential amplifier. As the touch sensor receives an induced electric field signal, the induced electric field signal is amplified by the differential amplifier and the signal judgment circuit determines whether the amplified induced electric field signal is a touch input.