In some MRI installations, there may be an offset in EDA measurements. The following steps can be performed in order to calibrate skin conductance measurements:
Install all cabling and place the EDA leads in the scanner, where they will be once the participant is there. The connection should be as follows: EDA leads->MRI cabling in chamber room to filter->Filter->MRI cabling from filter in control room->GSR100C amplifier.
The procedure involves performing a 2-point calibration with 2 known conductance values. You can record the voltage corresponding to conductance 0 (open leads) and conductance 10uMho (via placing a 100kOhm resistor between the leads) to calibrate the GSR100C amplifier. The GSR amplifier must be in DC mode (both high-pass filter switches should be set to DC). The following steps will guide you through the procedure.
MP menu->Set up channels and click on Setup for the GSR channel. Make sure the leads are open (nothing attached to the leads). Click on CAL1 and enter 0 for the Map value box for CAL1.
Attach a 100kOhm resistor between the leads and click on CAL2, enter 10 for the Map box for CAL2.
Set the units to uMho.
The amplifier will be calibrated for measurements in the scanner.
IMPORTANT! See Safety Guidelinesfor recording biopotential measurements in the MRI environment.
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