Something generated from outside the body. Electrodermal recordings that apply a voltage or current to the skin are called exosmotic and in polygraphy a direct current (DC) is used to measure aspects of EDA. Constant voltage DC systems record EDA as skin conductance (SC) for which the units are Siemens (S) or mhos, which is the inverse of an ohm in both spellings and in computation. Constant current systems measure and record skin resistance (SR), which is measured in ohms. EDL is the accepted abbreviation for electrodermal level and refers to the tonic or baseline level at any given moment, while EDR is reserved for the phasic response or reactions to stimulation. The designators R and L may be appropriately applied to the type of measurement taken, for example, SRR (skin resistance response) or SCL (skin conductance level). Both skin conductance and skin resistance are exosomatic measures because electrical currents are applied from outside sources to detect the electrodermal activity. As opposed to endosomatic. See: Handler, Nelson, Krapohl & Honts (2010).
