The measurement of micro sweating, in fact, an increase in sweating corresponds to a greater activation of the sympathetic nervous system, that is, the system that makes us "activate", which mobilizes our energy in the muscles and prepares us for action.
In fact, when the sympathetic nervous system is activated, the eccrine glands are activated and fill the sweat ducts and the saline properties of sweat modify the ability to conduct electricity. This type of glands are mainly concentrated on the palms of the hand and feet.
The sensors that are applied to measure skin conductance apply a very light electric current, then measuring the time taken to transmit the impulse from one electrode to the other. This measurement system, however, does not distinguish a positive or negative emotional activation but only highlights an activation of the nervous system. For this reason, skin conductance measures what in technical jargon is called arousal or the general activation we feel and the intensity of the emotion itself.