November 14, 2006
Galvanic Skin Response Sensor
I just finished building a galvanic skin response (GSR) sensor for two students who want to use it for a gaming study. The sensor measures the varying resistance of human skin, which is suppsedly a proxy for engagement in a game. I guess we'll have to wait for the results of their study to see how well this works.
The sensor has two probes that you strap around two fingers; a black plastic Fry's box where all the electronics live; and a USB connection to send sensor data to a PC.
Since you don't want to send a lot of current through your body, the sensor circuit is built around an op amp (LMC6442 single supply rail-to-rail), based on the schematics published by Michael Sung and Vadim Gerasimov here. I didn't have a 100k pot handy so I approximated with 3x20k pots and a 10k fixed resistor in series. Built on one of the super handy One Pas prototype boards. Output here is an analog voltage in the 0-5V range. This output is hooked to to and ADC port of a small d.tools board, which in turn sends data to a PC, but you can substitute your favorite PC interface here easily (Arduino, Phidgets, ...). On the PC, I graph results in Exemplar.
The finger probes were inspired by the Lego GSR Sensor page. I tried three types of probes: 3/4" copper foil tape on velcro (too thick, green fingers); 1/4" aluminum foil tape on velcro (glue not conductive); thumbtacks on velcro (preferred solution)
