What is GSR sensor | How does GSR sensor work

This page describes GSR sensor basics and its features and specifications. It mentions GSR sensor working operation or principle

Introduction: EDA (Electro Dermal Activity) refers to electrical characteristics of pores and skin. It include pores and skin conductance, GSR (Galvanic Skin Reaction), EDR (Electro Dermal Response) , PGR (Psych Galvanic Reflex) , SCR (Skin Conductance Response), SSR (Sympathetic Skin Reaction) and SCL (Skin Conductance Level). The principle of EDA is that pores/skin resistance varies with respect to state of sweat glands.

What is GSR sensor ?

Definition: The sensor which measures electrical conductance of our skin is known as GSR (Galvanic Skin Reaction) sensor. The electric conductance varies in proportion to moisture level of the skin. GSR value varies based on mental or physiological arousal as per sweating produced by our skin.

GSR sensor

GSR value is measured by placing electrodes appropriately at the fingertips usually index and middle fingers. The fingertips of these fingers have less skin thickness and hair presence. Hence it provides better results compare to other fingers. This is shown in the figure.

Following are the features of Grove GSR sensors V1.0 and V1.2 are manufactured by Seed Studio. This can be purchased from Tomson Electronics website.
• It is used to measure emotional arousal and to monitor sleep quality.
• It measures electrical properties of skin.
• It is based on electrical conductance which is equal to 1/resistance.
• It requires use of two electrodes on two fingers of one hand.

Technical specifications of Grove GSR sensors are as follows.
• Operating voltage : 3.3V/5V
• Sensitivity : Adjustable via a potentiometer
• Input signal : Resistance, not conductivity
• Output signal : Voltage, analog reading
• Finger contact material : Nickel

GSR sensor working operation

The conductive voltage of skin indicates different states of person's emotions viz. stressed or relaxed. The conductive voltage depends on sweat produced by the sweat glands which are controlled by nervous system. The conductivity of the skin changes due to sweat secretion and consecutively its voltage. The voltage is measured to determine states of emotions of human beings.

Let us understand working of GSR sensor.
➨In the relaxed condition of the person, sweat is not secreted and hence resistance of the skin is high. This results into lower conductive voltage.
➨In the physical arousal condition of the person, sweat is secreted and hence resistance of the skin is low. This results into higher conductive voltage.

GSR sensor interfacing

Following diagram depicts GSR sensor interfacing with Arduino board. Following are the connections between pins of both GSR sensor and arduino board.
Vcc (GSR sensor side) - 5V (Arduino side)
SIG - A0

GSR sensor interfacing with arduino

Refer GSR sensor interfacing >> which mentions arduino source code for GSR sensor testing.

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