Wearable Electrode Contact Detection via Differential Signal Multiplexing
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Solution Overview
Problem
Wearable electrocardiogram devices face challenges with high contact impedance and polarized voltage, leading to ineffective electrode contact state detection, false alarms, and increased manufacturing costs due to complex devices required for traditional lead-off detection solutions.
Innovation Solution
A contact state detection apparatus using a first and second electrode configured to receive an alternating current signal, outputting a differential signal for sampling, which includes a detection signal for physiological information and a signal to detect contact state, reducing device complexity and manufacturing costs by multiplexing the alternating current signal for simultaneous physiological and contact state detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional lead-off detection solution is used for wearable device, then electrode contact state detection can be performed, but manufacturing costs increase and device complexity increases
Solution Approach 1:
The patent applies multi-functionality by enabling the existing electrocardiogram detection electrodes and signal processing circuitry to perform both physiological signal detection and electrode contact state detection. The same differential amplifier and analog-to-digital converter used for ECG signals are repurposed to also detect contact impedance changes, eliminating the need for separate dedicated detection circuits and reducing overall device complexity while maintaining reliable contact state monitoring
2Reliability
If traditional lead-off detection solution is used for wearable device, then electrode contact state detection can be performed, but manufacturing costs increase
Solution Approach 1:
The patent reduces manufacturing costs by designing a system where existing components serve multiple purposes. The electrocardiogram detection circuitry, including differential amplifiers and analog-to-digital converters, is used for both physiological signal acquisition and contact state detection. This eliminates the need for additional dedicated hardware components, reducing bill of materials costs and simplifying the manufacturing process while ensuring reliable electrode contact monitoring
3Volume of moving object
If dry electrode with small area is used for wearable product, then volume and aesthetic factors are improved, but contact impedance between electrode and detected object becomes extremely high
Solution Approach 1:
The patent addresses the high contact impedance issue by changing the detection approach rather than modifying the electrode physical parameters. Instead of increasing electrode size or adding conductive gel, the system uses signal processing techniques including differential amplification and impedance measurement to detect contact states. The analog-to-digital converter samples the differential signal at multiple points to calculate contact impedance, allowing the system to maintain small dry electrodes while reliably detecting contact quality through electrical parameter measurement
4Volume of moving object
If dry electrode with small area is used for wearable product, then volume and aesthetic factors are improved, but detection accuracy deteriorates due to extreme contact impedance
Solution Approach 1:
The patent maintains detection accuracy with small dry electrodes by changing the detection parameters and signal processing approach. The system uses differential amplification to reject common-mode noise and measures contact impedance by analyzing the differential signal characteristics. The analog-to-digital converter samples at multiple time points to calculate impedance values, enabling accurate contact state detection despite the high contact impedance inherent to small dry electrodes
Solution Approach 2:
The patent introduces intermediate signal processing steps to bridge the gap between small electrode size and accurate detection. Differential amplifiers serve as intermediaries to extract useful signals from the high-impedance contact interface, and the sampling circuit acts as an intermediary to capture signal characteristics for impedance calculation. These intermediate processing stages enable accurate contact state detection without requiring larger electrodes
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 effectively reduces manufacturing costs and improves detection accuracy by distinguishing between physiological and contact state signals, enhancing signal-to-noise ratio and reducing interference, while maintaining effective electrode contact state detection in wearable devices.
Implementation Method 1
the second signal being a signal formed after the alternating current signal is modulated by the first electrode and the second electrode
Data Source
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AI summary
A contact state detection apparatus (100) and a wearable device. The contact state detection apparatus (100) includes: a first electrode (111) and a second electrode (112), both of the first electrode (111) and the second electrode (112) being configured to receive an alternating current signal and a first signal to output a differential signal, the differential signal including the first signal and a second signal, the first signal being a detection signal of physiological information of a detected object (110), and the second signal being a signal formed after the alternating current signal is modulated by the first electrode (111) and the second electrode (112); and a sampling circuit (121), the sampling circuit (121) being connected to the first electrode (111) and the second electrode (112), the sampling circuit (121) being configured to sample the differential signal to obtain a target sampling signal, and the target sampling signal including a first sampling signal corresponding to a first signal and a second sampling signal corresponding to the second signal. The contact state detection apparatus (100) could reduce costs on the basis of solving a problem of losing effect of electrode detection due to high contact impedance or polarized voltage.