Electrode–skin impedance imbalance measured in the frequency domain
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Objective To measure the magnitude and phase imbalance of the electrode-skin interface for silver/silver chloride (Ag/AgCl) and silver (Ag) electrode pairs, highlighting the need to balance both the magnitude and phase of the electrode-skin interface. Methods The electrode-skin impedance imbalance between two electrodes placed on ten healthy subjects was recorded over a frequency range of 1 Hz–100 kHz, using three electrode configurations: Ag/AgCl electrodes without skin preparation (Ag/AgClNSP), Ag/AgCl electrodes with skin preparation (Ag/AgClSP), and Ag electrodes with skin preparation (Ag-SP). A compensation network was developed to simulate impedance imbalance reduction using the experimental data. Results The mean electrode-skin impedance imbalance at 50 Hz was (37.6 ± 47.1) kΩ and (15.0 ± 18.3) degrees using the Ag/AgClNSP electrode configuration; (4.52 ± 7.65) kΩ and (4.6 ± 6.9) degrees using the Ag/AgClSP electrode configuration; and (36.2 ± 45.1) kΩ and (3.4 ± 3.6) degrees using the Ag-SP electrode configuration. The compensation network resulted in a mean reduction in impedance imbalance over the bioelectrical signal range (1 Hz–500 Hz) of 284.3 kΩ and 11.9 degrees; 4.6 kΩ and 6.2 degrees; 86.7 kΩ and 2.5 degrees for the Ag/AgClNSP, Ag/AgClSP and Ag-SP electrode configurations respectively. Conclusion This study confirmed that the electrode-skin impedance imbalance can be large, and varies between subjects. Although abrasive skin preparation reduces the electrode-skin impedance imbalance, it does not guarantee a balanced electrode-skin interface, therefore, balancing the electrode-skin impedance using a compensation network has the potential to decrease bioelectrical signal interference. Significance As bioelectrical signal interference is a function of electrode-skin impedance imbalance, to improve noise immunity of bioelectrical signal recordings, added compensatory impedance is required to balance the electrode-skin interface.
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ANZSRC fields of research
0906 Electrical and Electronic Engineering
1004 Medical Biotechnology
Fields of Research::32 - Biomedical and clinical sciences::3206 - Medical biotechnology::320602 - Medical biotechnology diagnostics (incl. biosensors)
Fields of Research::40 - Engineering::4003 - Biomedical engineering::400305 - Biomedical instrumentation
Fields of Research::40 - Engineering::4008 - Electrical engineering::400899 - Electrical engineering not elsewhere classified