info@biopac.com
support@biopac.com
www.biopac.com
BIOPAC Hardware | SS3LA | Page 1 - 2 Updated: 7.16.2012
SS3LA EDA (ELECTRODERMAL ACTIVITY) TRANSDUCER
The SS3LA transducer connects to a single MP3X input channel to record electrodermal
activity (skin conductance or, with proper setup, skin resistance). Two Ag-AgCl electrodes are
mounted in individual, ergonomically designed, polyurethane housings for improved contact.
They attach to the fingers by a Velcro strap or can be taped to any other part of the body. The
electrodes have a 6 mm contact area with a 1.6 mm cavity to accommodate electrode gel
(GEL1, GEL101, or the preferred recording gel). The non-polarizable electrodes are shielded to minimize noise
interference and improve recordings. These electrodes are different from standard SS2L electrodes in that they
have built-in, reusable electrodes on the end, the electrodes are specially designed to fit around the tip of a
person’s finger, and the electrodes measure only one type of signal—the EDA.
See the SS57L EDA (GSR) Lead for a disposable electrode option
USAGE RECOMMENDATIONS
Setup - There must be good electrical connections between the skin and the electrodes for EDA to work properly.
Gel - When using GEL101 isotonic gel it is important that the gel has a chance to be absorbed and make good
contact before recording begins. Accordingly:
1. Apply GEL101 to the skin at the point of electrode contact and rub it in.
2. Fill the SS3LA electrode cavity with GEL101.
3. Attach the SS3LA electrode to the subject.
4. Wait 5 minutes (minimum) before starting to record data.
Presets - BSL PRO software includes two EDA presets:
Electrodermal Activity (EDA), 0 - 35 Hz; requires calibration—see details below
Electrodermal Activity (EDA) Change; no calibration required
To calibrate the SS3LA using the Electrodermal Activity (EDA), 0 - 35 Hz preset:
1. Prepare two 1% calibration resistors; 100 kiloohm and 1 megaohm. Insulate the resistor using clear
tape such that when held, the fingers will not directly contact the resistor leads.
2. Place the 1 megaohm resistor such that one resistor lead contacts one electrode pad and the other
resistor lead contacts the opposite electrode pad.
3. From the Scaling dialog box, set the Cal1 Scale value to “1” and click Cal1.
4. Repeat step 2 using the 100 kiloohm resistor.
5. From the Scaling dialog box, set the Cal2 Scale value to “10” and click Cal2.
Gain - verify the Gain setting of the SS3LA:
1. From the Scaling dialog box, set the Cal1 Scale to "0" and click Cal1.
2. Set the Cal2 Scale to 5Mho/V and the Input voltage to 1 V, and then close out of the Scaling dialog box.
3. Insulate a 100 kiloohm resistor and place it from electrode pad to electrode pad (resistor must be insulated
from fingers).
4. Perform measurement with electrode-resistor setup.
BSL PRO should
produce a reading of 10 microsiemens
(older presets may use micromhos units
label)
.
*SCR - Use an Expression calculation channel to take reciprocal of conductance, and then apply proper scaling.
Tip
To detect a good signal, subjects should have a little sweat on their hands (not a lot, but
enough so that their hands are not completely smooth or cold). If subjects wash their
hands just prior to the recording or if they have been sitting in a cold room, then they
must do something to activate the sweat glands before beginning calibration or
recording. If subjects begin with colder hands, the scale will be diminished and the signal
will be easily saturated once they “warm up” during the lesson.
To Next Page
Loading...