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Comparison of electrodermal constant voltage and constant current recording techniques using the phase angle between
1Department of Physiological Psychology, University of Wuppertal, Germany.
Psychophysiology
|March 8, 2000
Summary
Direct current electrodermal activity recordings show level-dependent variations. Using alternating current and measuring phase angle changes resolves this issue, providing equivalent results across different electrodermal levels and preventing electrode polarization.
Area of Science:
- Psychophysiology
- Biomedical Engineering
- Electrophysiology
Background:
- Direct current (DC) electrodermal activity (EDA) recordings exhibit measurement dependencies on the electrodermal level (EDL).
- Constant voltage and constant current methods yield different electrodermal reaction patterns when using DC measurements.
- This EDL dependency complicates the interpretation of electrodermal responses in psychophysiological research.
Purpose of the Study:
- To investigate an alternative method for electrodermal activity recording that overcomes EDL dependency.
- To evaluate the efficacy of using alternating current (AC) and phase angle changes for electrodermal recording.
- To compare AC phase angle measurements with conventional DC methods under varying EDLs.
Main Methods:
- Forty subjects participated in a 20-trial habituation series under controlled room temperature variations.
- A multiplexing system enabled quasi-simultaneous recording of electrodermal activity using both constant current (CC) and constant voltage (CV) modes.
- Measurements were performed under both direct current (DC) and alternating current (AC) conditions, with AC responses analyzed as phase angle changes.
Main Results:
- Electrodermal recordings using the AC phase angle method yielded equivalent results for CC and CV measurements.
- This equivalence was maintained even when significant electrodermal level variations were induced.
- The AC phase angle method successfully eliminated the differential level dependency observed in DC recordings.
Conclusions:
- The phase angle method utilizing alternating current provides a robust solution to the electrodermal level dependency problem in electrodermal recording.
- This technique offers equivalent and reliable electrodermal measurements across varying electrodermal levels.
- An additional benefit of the AC phase angle method is the prevention of electrode and skin polarization.