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Biomedical Instrumentation Lab Lab Experiments

Galvanic skin resistance measurements


To measure the pH of a given sample

Apparatus Required:

  1. GSR Simulator
  2. GSR instrument
  3. Electrode
  4. DSO


  1. Connect the GSR meter to the main supply
  2. Connect the resistance simulator to GSR meter
  3. Set the resistance in simulator to 10 k ohms
  4. Adjust the GSR meter to zero.
  5. Increase the resistance value in simulator
  6. Record the GSR meter and tabulated
  7. Increase the resistance in simulator step wise and measure the deflection and tabulated.
  8. Connect the electrodes in finger
  9. Connect the output of electrodes to GSR meter
  10. Measure the resistance change
  11. Ask the patient for different emotions and record the change in GSR value.
  12. Connect the DSO with GSR meter
  13. Get the waveform of chages in GSR with respect to time.


Human skin offers resistance to electric current just like a resistor do in an electronic circuit. This transient change in the electrical conductivity of the skin followed by an arousal or oriented response is referred to as Galvanic skin response or GSR .The skin acts as a resistive layer and readily passes electric current. In normal Skin tone, the resistance varies from 25 Kilo Ohms to a few Mega Ohms. This permits little current to pass through it. Sweating in the high emotional state or stress causes increased blood flow to the skin and reduces the skin resistance and increases its electrical conductivity.

Electrodermal activity (EDA), is the property of the human body that causes continuous variation in the electrical characteristics of the skin. Historically, EDA has also been known as skin conductance, galvanic skin response (GSR), electrodermal response (EDR), psychogalvanic reflex (PGR), skin conductance response (SCR), sympathetic skin response (SSR) and skin conductance level (SCL). The long history of research into the active and passive electrical properties of the skin by a variety of disciplines has resulted in an excess of names, now standardized to electrodermal activity (EDA).[1][2][3]

The traditional theory of EDA holds that skin resistance varies with the state of sweat glands in the skin. Sweating is controlled by the sympathetic nervous system,[4] and skin conductance is an indication of psychological or physiological arousal. If the sympathetic branch of the autonomic nervous system is highly aroused, then sweat gland activity also increases, which in turn increases skin conductance. In this way, skin conductance can be a measure of emotional and sympathetic responses

area of skin under electrode

Procedure:Skin conductance (SC) is normally measured with 8mm diameter silver/silver chloride electrodes positioned on the medial phalanx of the index and middle fingers held in position by double sided sticky electrode collars. A non-saline jell is used. SC response (SCR) provides an indication of arousal.

Electrode placement for measurement of GSR is as shen in the fig. The output of electrode is given the op amp input as shown in the circuit diagram. The output of the amplifier if given to CRO to display the variations of skin resistance with respect to time. The sample waveform is as shown in the figure

a simple gsr signal of 60 seconds duration

Electrode placement diagram:

electrode placement diagram

Tabular Colum       Basal Skin Resistance

S.No. Simulator Skin resistance Theoretical GSR Measured GSR


The galvanic skin resistance was recorded and analyzed the GSR for various emotions