Capacitive ECG Mat for Contactless Signal Acquisition
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Solution Overview
Problem
Conventional ECG electrodes face challenges such as poor signal-to-noise ratio, skin irritation, and difficulty in accurate placement, especially for hairy subjects or those with skin conditions, and contactless electric potential sensors struggle with external interference and signal processing.
Innovation Solution
An electrocardiographic device featuring electric potential sensors integrated into insulating user interaction regions, with movement sensors to filter out hand vibrations, and a configuration allowing optimal sensor placement for improved signal quality, enabling contactless ECG signal acquisition through multiple leads without adhesives or conductive gels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wet electrodes with conductive gel are used, then good electrical contact is achieved, but skin irritation and discomfort occur
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the capacitive electrode and the skin. This mediator enables capacitive coupling for electrical signal detection while preventing direct contact that causes skin irritation. The insulating layer acts as a barrier that allows the useful function (electrical coupling) while eliminating the harmful effect (skin irritation).
Solution Approach 2:
The patent replaces the mechanical contact-based electrode system (wet electrodes requiring direct skin contact and adhesive application) with a capacitive coupling system. This substitution eliminates the need for mechanical attachment and conductive gel application, thereby removing the source of skin irritation while maintaining electrical signal detection capability.
2Object-affected harmful factors
If conventional dry electrodes are used, then no skin irritation occurs, but signal to noise ratio becomes very high
Solution Approach 1:
The patent changes the operational parameters of the electrode system by using capacitive coupling instead of direct electrical contact. This parameter change enables the system to achieve both low skin irritation (by maintaining physical separation) and improved signal-to-noise ratio (by optimizing the capacitive coupling distance and using differential amplification to reject common-mode noise).
Solution Approach 2:
The patent employs differential amplification as a feedback mechanism to reject common-mode noise. By measuring the potential difference between two capacitive electrodes and using differential amplification, the system selectively amplifies the desired ECG signal while rejecting environmental noise and interference, thereby improving the signal-to-noise ratio without requiring direct skin contact.
3Measurement precision
If accurate electrode placement is required for proper ECG signal acquisition, then measurement precision improves, but ease of operation deteriorates due to difficulty in locating correct positions
Solution Approach 1:
The patent uses visual indicators (such as colored markings or illuminated guides) on the mat to indicate the correct placement positions for the capacitive electrodes. These visual cues change or become apparent when the user is in the correct position, providing immediate feedback that simplifies the placement process while ensuring measurement precision.
Solution Approach 2:
The patent designs the system so that the user's own body position or movement automatically brings them into the correct electrode placement position. For example, the mat may have sensors that detect when the user is properly positioned, or the electrode positions are designed to align naturally with anatomical landmarks, allowing the user to self-correct their placement without external assistance.
4Ease of operation
If contactless electric potential sensors are used, then user comfort and ease of use improve, but susceptibility to external interference increases
Solution Approach 1:
The patent uses differential amplification and common-mode rejection as feedback mechanisms to eliminate external interference. By measuring the potential difference between two capacitive electrodes and using differential amplification, the system selectively amplifies the desired ECG signal while rejecting environmental noise and interference, thereby maintaining user comfort while improving signal quality.
Solution Approach 2:
The patent extracts and eliminates the harmful component (common-mode noise and external interference) from the signal by using differential measurement techniques. By measuring only the potential difference between electrodes and rejecting the common-mode component, the system removes external interference while preserving the useful ECG signal, maintaining both user comfort and signal quality.
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 device achieves high signal quality and reduced noise levels, allowing for accurate cardiac activity monitoring with improved user comfort and ease of use, capable of capturing multi-lead ECG signals effectively through thick skin and clothing.
Implementation Method 1
contactless electric potential sensors struggle with external interference and signal processing... These electrodes, commonly referred to as electric potential sensors, work by sensing the electric field created by displacement currents in the body of the subject
Implementation Method 2
a movement sensor configured to provide a movement signal that, in use when a user's hands are in the first position, represents movement and/or vibration of the user's hands
Data Source
AI summary
An electrocardiographic device for sensing cardiac activity in a user comprising: a first set of electric potential sensors; and a first set of indicia indicating a first position of a user's hands with respect to the first set of electric potential sensors; wherein the first set of sensors are arranged relative to the first set of indicia such that, in use when a user's hands are in the first position, an electric potential sensor is located under the thenar eminence and/or an electric potential sensor is located under the hypothenar eminence of each of the user's hands.