Galvanic skin response sensors (GSR sensors)

The electrical activity of skin (EAS) formerly named galvanic skin response (GSR). In fact, the GSR is a bioelectric reaction, which is an indication of the activity of autonomic nervous system (ANS). The process of sweating is meant for thermoregulation of the body, and appears when you change the level of psycho-emotional stress. Due to the fact that the ANS activity cannot be consciously corrected, EAS sensor indications refer to a high level of reliability.

Design features of GSR sensor

In Rubicon polygraph:

  • EAS is registered from skin surface by bipolar non-polarizing electrodes via "GSR" sensor (marked "K" or "GSR").
  • Fere method is applied with the application of external current (exosomatic method), indicators of which are considered to be skin conductance (SC) and skin resistance (SR).
  • Current measuring circuit - 2 microamps.
  • Operating measurement ranges from 2 to 1500 kOhm.
  • The sensor contains two reusable electrodes for placement on various phalanxes of fingers. Electrodes can be placed on the palmar surface, for which the sensor is additionally equipped with two-sided Velcroes - Velcro-type extensions of 25 centimeters in length.
  • Two types of electrodes of the same area and the diameter of curvature are used:
    1. brass base with 24 karat silvering of 25 microns thick contact surface;
    2. base made of stainless steel with 24-carat gilding of 25 microns thick contact surface.

Specifics of GSR sensor application

Skin conductivity - the so-called "fast", "phasic" component which characterizes the phase of response reaction of the central nervous system for situational stimulus (stimulus question), which proceeds within 2-3 to 7-8 seconds (depending on the reactivity type of a person).

In software the skin conductance (SC) is represented in graphical form with measuring frequency indicator no less than 16 times per second. SC indications are to be interpreted in such a way:

  • the positive part of the amplitude as a degree of importance, as well as the magnitude of the reaction to novelty;
  • the negative part of the amplitude as a degree of functional reserve for conduction of research procedures.

Skin resistance - the so-called "slow", "tonic" component which characterizes the tone of psycho-emotional stress, which varies within 2-3 minutes (depending on the degree of importance of aspect / topic / research conditions).

In software the skin resistance (SR) is represented in digital form with measuring frequency indicator no less than 1 time per second. SR indications are to be interpreted in such a way:

  • as a level of optimality of psycho-emotional stress for the research (in terms of digital values);
  • as a degree of importance of question-stimulus (according to the change of averaged digital values during the period of physiological reaction).

Notes on the GSR sensor:

  • SR indications "2048" indicate poor connectivity of the sensor to the unit of data collection and processing, or that the sensor is not functional.
  • Digital SR minus values indicate of excessive psycho-emotional stress of a person or inversion indications of registration channel (way to eliminate the phenomenon of inversion is presented in the user's manual).