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Ag-AgCl electrode noise in high-resolution ECG measurements
1Departament d'Enginyeria Electrònica, Universitat Politècnica de Catalunya, Barcelona, Spain. mireya@eel.upc.es
Biomedical Instrumentation & Technology
|May 23, 2000
Summary
Researchers measured noise and impedance for silver-silver chloride (Ag-AgCl) electrodes used in high-resolution electrocardiogram (ECG) measurements. Electrode noise is typically higher than thermal noise and influenced by various factors, but offset voltage can help identify low-noise electrodes.
Area of Science:
- Biomedical Engineering
- Electrophysiology
- Signal Processing
Background:
- High-resolution electrocardiogram (ECG) measurements require low-noise electrodes.
- Silver-silver chloride (Ag-AgCl) electrodes are commonly used in ECG.
- Understanding electrode noise and impedance is crucial for signal quality.
Purpose of the Study:
- To measure and characterize noise and impedance of Ag-AgCl electrodes.
- To compare electrode noise with thermal noise from electrode impedance.
- To identify factors influencing electrode noise and methods for noise identification.
Main Methods:
- Simultaneous measurement of electrode noise and impedance.
- Testing Ag-AgCl electrodes in face-to-face configuration and on human body surface.
- Analysis in the frequency band of 0.5 Hz to 500 Hz.
Main Results:
- Electrode noise depends on electrode area, electrolytic gel, patient, and placement site.
- Root-mean-square electrode noise is typically <1 microV (face-to-face) and 1-15 microV (body surface).
- Noise spectral density increases at low frequencies (1/f^a) and exceeds thermal noise.
Conclusions:
- Electrode noise is a significant factor in high-resolution ECG, exceeding thermal noise.
- Electrode noise is influenced by multiple physical and biological factors.
- DC offset voltage measurements correlate with electrode noise, aiding in identifying low-noise electrodes.