EDA or ElectroDermal Activity measures skin conductivity with 2 electrodes placed on each finger (of the same hand). Actually we do not quite need electrodes, simple jumper cables (holding wires made of copper and aluminum) suffice to be in contact with our skin. One finger receives tiny current which flows to the other finger as well, and their conductivity rises with perspiration because more electrolytes or salt is secreted.

This technique is based on the paper from MIT: Poh et al. A wearable sensor for unobtrusive, long-term assessment of electrodermal activity. IEEE Transactions on Biomedical Engineering

What you need to make it work:

  • Arduino UNO (ATMega328P)
  • Operational Amplifier (LM358) or any other equivalent e.g. TLC2272
  • Four resistors (three of 100K and one of 1M)
  • Four capacitors 0.1uF
  • A lot of jumper cables

See more in my personal web page https://jmladeno.net/