EDA – skin sensing

This is ‘electro-dermal activity’ or what used to be called ‘galvanic skin response’ basically a measure of sweat.  It is the same technique as used by a lie detector.  When you are under stress, when you get a shock or in general at a heightened level of emotion or activity your skin gets more sweaty and skin resistance decreases.
The sensor used for this was an Affectiva Q wrist-worn device developed originally by Picard’s Affective Computing group in MIT, then commercialised.  Unfortunately it is now out of production, but the Q sensor resources page is still available explaining its operation. The device also measures skin temperature and has three-axis accelerometer.
The sensor is placed on the underside of the wrist, the opposite way round to a wrist watch, and the sensors face the skin.  I always wore it on my left wrist.
meta information, one line per file, mostly one day per file
on one occasion there are two files in one day  where I accidentally knocked the device off and then had to start it again
name – file name
url – dropbox url
sampling_rate – always 8 = samples per second
timeset – ignore files where timeset = false, it means I did something wrong!
start_date – \ ___ date and time when recording starts
start_time – /
offset – always +1 I think this means BST rather than GMT
number_of_samples – number of data samples divide by 8 to get duration in seconds
identical data in JSON format
Each EDA file contains 8 lines of header information followed by data starting at line 9:
data columns:
Z-axis             –    \
Y-axis             –     > —-  accelerometer data … in principle could get paces from this …
X-axis             –    /
Battery            –   battery level – ignore
ÔøΩCelsius    –  skin temperature in degrees
EDA(uS)         –  EDA in whatever they measure it in!!  bigger means more emotion/stress/sweat
Note this is a CSV export from the raw EDA files produced by the Q sensor.

Extract of CSV meta file


Extract of EDA data file (CSV export)

Log File Created by Q Live - (c) 2012 Affectiva Inc.
File Version: 1.01
Firmware Version: 1.71
Sampling Rate: 8
Start Time: 2013-05-08 09:16:30 Offset:+01
 Z-axis | Y-axis | X-axis | Battery | �Celsius | EDA(uS)