GSR - Galvanic Skin Response

[last updated: 2025-08-22]
Disclaimers
bioAmp EXG pill
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      On This Page:
• Introduction
• Circuit configuration options
• Finger probes
• ...
• Links
• Introduction:
  GSR is the resistance of your skin. The actual value of the resistance varies from several megOhms for dry skin, to ??? a few hundreds of kOhms for damp, sweaty skin.
  The sweat that affects your skin resistance is much more subtle than what we think of as perspiration or "sweating." It happens almost instantaneously as your mental state changes, and is mostly affected by your stress level.

  
  As such, its two most common usages are

  • in biofeedback, to help a person relax,
  • and as a lie detector.

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• Circuit configurations:
  • Several different circuit configurations/approaches are suggested in different places on the web. Broadly, ...
    • Connect GSR resistance probe in series with a fixed resistor to create a voltage divider between +V and gnd,
      and then process (amplify and filter) the resulting varying analog voltage in some circuit.
      • directly into arduino analog input (after op-amp voltage follower to give the arduino the low input impedance it requires)
      • various op amp filter and amplifier circuits...

      • Key point:
        Some sites used straight analog signal (perhaps amplified and filtered)
        while others used the differential, only responding to changes in the signal.
    • Use the GSR resistance directly in some circuit, eg. the transistor oscillator (if I can find the link...)

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• Finger probes:
  • from instructables link below...
  • briefly, a strip of velcro, 3/4" x 4"? long
    remove backing to expose the sticky side
    strip a lead wire and splay the bare wires and stick them to the sticky side of the velcro
    cover all of the sticky side of the velcro including the wire with tin foil, trim to fit.
    cut 1/2" x 1/2" piece of velcro "latch" strip and put onto the tin foil side of your strip
        instructions said to put it on the opposite end of the strip from the electrodes,
        but it made more sense to me to put it on the same end.
    done
  • Built as such, on index and middle fingers, mine read nom. 400-900k.

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• Differential Input op-amp circuit:
  • I built the circuit shown in Chris3000 link below, using LM324 quad op amp and a 3.87 Li battery (instead of 1.5v he used).
    It worked. Output voltage on the order of 2 - 3v, adjustable from the two pots.
  • There are two control pots in the circuit:
    • a 1M pot in series with the finger probes, calling it an "offset" pot,
    • and a 100k pot between the two differential inputs to the op-amp circuit, calling it a "balance" adjustment
  • Testing:
    With a fixed 1M resistor connected in place of the finger probes,
    with the "balance" 100k pot about mid-range,
    the "offset" pot varied the output voltage between 1.85v and 2.9v.
    • My circuit analysis skills are insufficient to know why/how to adjust these two controls,
      so I just leave them about mid-point.
  • Operation/evaluation:
    • The circuit is configured such that a higher input resistance from the finger probes
      will give a higher output voltage.
    • This means, for common operation as a biofeedback device,
      in which a relaxed state gives higher skin resistance,
      the goal of a meditative practice would be to increase the circuit's output voltage.

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  • Links:
    • finger probes - good, with lots of slow, boring irrelevant stuff, but general idea is great:
      https://www.instructables.com/Making-Galvanic-Skin-Response-Finger-Elect...
      youtube: https://www.youtube.com/watch?v=ljVQpwVHpOo
    • very rough and incomplete, some python scripts for filtering:
      https://github.com/Noura/diy-gsr
    • interesting differential input op-amp circuit:
      https://www.chris3000.com/galvanic-skin-response/
    • some common sense tips, mostly worthless:
      https://imotions.com/blog/learning/best-practice/essentials-galvanic-ski...
    • investigate this - inst op amp with amplification and filtering and differentiation
      to respond to changes in GSR:
      https://community.element14.com/members-area/b/blog/posts/ouch-sensing-g...
    • Seeed Grove GSR Sensor:
      https://wiki.seeedstudio.com/Grove-GSR_Sensor/
    • investigate this - transistor oscillator circuit:
      https://www.homemade-circuits.com/gsr-meter-circuit-for-biofeedback-meas...
    • summary page for polygraph project/kit (using GSR, breath & pulse rates), with links:
      https://hackaday.com/2019/12/25/arduino-polygraph-shows-how-its-done/
    • using "GSR Sensor":
      https://docs.cirkitdesigner.com/component/edcd3277-e89b-4dd7-b79b-7b1a38...
    • worthless: https://www.youtube.com/watch?v=1SjEw8J4ZbQ
    • mostly worthless, maybe some good ref material to products:
      https://support.mindwaretech.com/knowledge-base/kb0096/
    • https://www.instructables.com/Galvanic-Skin-ResponseGSR/
    • https://community.element14.com/members-area/b/blog/posts/ouch-sensing-g...
    • https://forum.arduino.cc/t/amplifying-a-simple-gsr-signal/246273
    • https://forum.arduino.cc/t/galvanic-skin-response-gsr/504512
    • https://forum.arduino.cc/t/how-to-convert-analog-data-in-gsr-sensor/1111702
    • https://forum.arduino.cc/t/skin-conductivity-circuit-help-pls/475103
    • https://thomaskosch.com/index.php/2017/12/17/galvanic-skin-response-powe...
    • https://www.dfrobot.com/blog-431.html?srsltid=AfmBOorFMDuavL9ItLRi-lqPDU...
    • uses "GSR Sensor" from Seeed?: https://www.instructables.com/Galvanic-Skin-ResponseGSR/
    • https://www.instructables.com/Simple-Polygraph-With-Arduino/
    • https://www.reddit.com/r/AskElectronics/comments/ncu5dd/i_need_to_build_...
    • https://www.youtube.com/watch?v=1clagERAiR4
    • worthless: https://keithdewey.com/articles/innovation/galvanic-skin-response-gsr-se...
    • https://www.kpkaiser.com/mindhack/hacking-meditation-with-the-arduino/

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