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Common-Mode Voltage Reduction in Capacitive Sensing of Biosignal Using Capacitive Grounding and DRL Electrode
Tadeas Bednar1, Branko Babusiak1, Michal Labuda1
1Department of Electromagnetic and Biomedical Engineering, University of Zilina, 01026 Zilina, Slovakia.
Sensors (Basel, Switzerland)
|April 30, 2021
Summary
Capacitive biosignal monitoring is comfortable but susceptible to power-line noise. An active capacitive Driven Right Leg (DRL) electrode effectively reduces this noise, offering better performance and lower cost than passive grounding electrodes for wearable health devices.
Area of Science:
- Biomedical Engineering
- Signal Processing
- Wearable Technology
Background:
- Capacitive biosignal measurement offers comfortable, unobtrusive long-term health monitoring.
- Wearable biosensing systems are highly susceptible to environmental noise, particularly power-line interference.
- Power-line noise manifests as common-mode voltage, degrading signal quality in capacitive sensing.
Purpose of the Study:
- To investigate methods for reducing power-line noise in capacitive biosignal acquisition.
- To compare the effectiveness of a passive capacitive grounding electrode versus an active capacitive Driven Right Leg (DRL) electrode.
- To evaluate the impact of electrode size on noise suppression and the cost-efficiency of different noise reduction techniques.
Main Methods:
- Modeling and experimental verification of two noise reduction techniques: passive capacitive grounding and active capacitive DRL electrode.
- Systematic investigation of the effect of grounding electrode size on power-line noise suppression.
- Comparative analysis of noise attenuation efficiency between grounding and DRL electrodes at power-line frequencies.
Main Results:
- Increasing the area of the grounding electrode significantly reduces power-line noise, with noise power decreasing from 70.96 dB to 43.44 dB as area increases from 1650 cm² to 4950 cm².
- The active capacitive DRL electrode demonstrates superior common-mode noise rejection compared to the passive grounding electrode.
- At an electrode area of 1650 cm², the DRL electrode achieved 46.3 dB greater attenuation of power-line noise than the grounding electrode.
Conclusions:
- The active capacitive DRL electrode is more effective for common-mode noise rejection in capacitive biosignal monitoring than passive grounding electrodes.
- The DRL electrode offers a more cost-effective solution due to its smaller electrode area requirement, especially when using expensive conductive textiles.
- These findings support the development of more robust and affordable wearable health monitoring systems by mitigating power-line noise interference.
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