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Electrodermal activity measurements


EDA = electrodermal activity
SRR = skin resistance response

SRL = skin resistance level

SCR = skin conductance response

SCL = skin conductance level

SPR = skin potential response

SPL = skin potential level


SRR and SCR are reciprocals of each other but are otherwise the same thing – discrete changes in skin resistance/conductance. To measure ONLY these changes, data may be acquired through a high pass filter.  The EDA100C (older model: GSR100C) has 0.05Hz and 0.5Hz HP filters which may be used for this purpose.


SRL and SCL are similarly reciprocols but otherwise the same thing – the baseline skin resistance/conductance. To record this form of activity, data must not be high pass filtered.  EDA100C (GSR100C) must be set up with both HP filter switches in the “DC” positions. 


NOTE: Recording DC signals does NOT prevent the recording of SCRs.  However, limiting the acquired data by passing it through a high pass filter for the purpose of recording ONLY SCRs prevents the recording of tonic SCL.  To take advantage of all EDA analysis features in AcqKnowledge or, more generally, to fully characterize EDA, SCL must be recorded, so HP filters should both be set to DC. 


While SRR, SCR, SRL and SCL rely on an external source of current (they are exosomatic), SPR and SPL do not (they are endosomatic). The EDA (GSR) series amplifiers are not appropriate for measuring SPR and SPL. (If you wish to work with these measures please contact support at BIOPAC for details.)


Skin conductance is usually measured in micromhos. Conductance is the reciprocal of resistance. 1 micromho of SCL is equivalent to 1,000,000 ohms SRL. The siemens and mho (as well as units derived from them such as microsiemens and micromho) are different names for the exact same unit.

Source: Psychophysiology Human Behavior and Physiological Response Fourth Edition
John L. Andreassi, Baruch College City University of New York,



Page last modified 24Dec2014

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