Differential GSR Amp

by Carson Reynolds

Over the last week I built and tested a new GSR amp that was based on a design by Tad Hirsch. The new design uses a differential amplifier with a gain of 100 to compare two voltage dividers: one which drops through electrodes across the skin and a second which drops through a 1 Mega Ohm potentiometer. This design works rather well and I’ve informally tested it on at least 5 other people. I get voltage swings at the output of above 1 V when people are at a resting state and then hyperventilate. Going forward I’d like to maybe add some filtering, but definitely add a voltage controlled resistor in place of the potentiometer.