Wearable Biosensor Ground Tracking With Current Compensation
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Solution Overview
Problem
Biosensing applications face challenges due to external interference and noise causing deviations in ground potential, leading to common mode interference and reduced accuracy in devices using dry electrodes.
Innovation Solution
Implementing a ground tracking system with a reference electrode to measure the difference between device and body potential, and using a current-compensation circuit to generate a compensating current, thereby maintaining the voltage across a current sense resistor at zero volts, thus canceling noise currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ground tracking is implemented to reduce interference, then measurement precision is improved, but device complexity increases
Solution Approach 1:
A ground electrode is introduced as an intermediary element to sense currents from interference sources. This mediator enables the system to detect and compensate for ground potential deviations without requiring complex direct measurement circuits, thus improving measurement precision while controlling device complexity
Solution Approach 2:
The system implements feedback by using the ground electrode to sense interference currents and providing compensating currents of equal but opposite direction. This feedback mechanism continuously adjusts to maintain accurate biosignal detection, resolving the contradiction between improved precision and increased complexity through intelligent control
2Measurement precision
If current compensation is applied to eliminate noise, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The current compensation circuit applies partial action by only compensating for the specific interference currents detected by the ground electrode, rather than continuously applying maximum compensation. This selective approach reduces power consumption while maintaining effective noise reduction and measurement precision
Solution Approach 2:
The system employs self-service through automatic current compensation where the circuit autonomously detects interference currents and generates compensating currents without requiring external intervention. This self-regulating mechanism optimizes energy usage by activating compensation only when interference is present, balancing power consumption with noise reduction effectiveness
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
This approach enhances the accuracy and precision of biosensing systems by reducing and eliminating noise interference, providing stable and precise biosignal detection.
Implementation Method 1
senses the current from noise sources using a current sense resistor
Implementation Method 2
a buffer is positioned between the current sense resistor and compensation circuit in order to cause the compensation current to flow through the user's body to the ground electrode
Data Source
AI summary
Methods and systems for ground tracking and current compensation for biosensing systems are described. In one aspect, a wearable device includes a wearable structure configured to be worn by a user, the wearable structure having an interior surface and an exterior surface, the interior surface being configured to face a user's skin while the wearable device is being worn by the user. The wearable device further includes an electrode at a first position on the interior surface, the electrode configured to detect biopotential signals of the user; and a reference electrode at a second position on the interior surface. The wearable device is configured to (i) measure, via the reference electrode, a difference between a ground potential of the wearable device and a body potential of the user, and (ii) compensate for the difference in processing of the biopotential signals detected by the electrode.