Understanding the EDA / GSR sensor on the Versatile Bio
What it measures:
The electrodermal activity / galvanic skin response sensor measures the admittance (inverse of resistance) across the skin, which changes with perspiration and is analogous to emotional arousal.
Psychology, neuroscience, human factors, user experience, market research, etc.
How to use:
There are two sensors, each one is usually attached via Velcro strap to the middle and ring-fingers of the non-dominant hand.
Note that, because resistance measured will change with different sensor locations, we recommend positioning the sensors in the same place on all participants within a study.
How to clean:
Clean the wiring, body and sensor ends with mild soap and water. Avoid getting the connectors wet. Allow the senors and all wiring to dry completely before use.
Autoclave is not recommended.
Connector on Versatile Bio:
Right-click on wave view in Bitbrain Device Viewer to view data-visualization filter settings.
Under "Notch-Filter" we recommend setting this to the preset matching your country's AC frequency (presets exist for USA/Japan at 60 Hz, and Europe at 50 Hz).
Under "Other Filter" click "enabled"
Set filter type to "Bandpass"
Set High (Hz) to 10
Set Low (Hz) to 0.2
Type is "Butterworth"
Order set to 4
Data for the EDA sensor is reported as analog voltage in µV (V analog in the formula below).
To calculate GSR resistance in ohms (), use the following formula, where (V analog) is the µV value reported by the Versatile Bio on the channel the EDA sensor is set up on:
To calculate GSR admittance in siemens (), use the output from the previous formula in the following formula:
In MS excel, the conversion formula would look like this (analog µV values in column A, enter formula between [ ] marks into B1 and C1):
A1 = Recorded (analog V) value
B1 = [=6490000/((3.3/G3)-1)]
C1 = [=1/B1]
B1 = GSR Resistance in ohms
C1 = GSR admittance in siemens