EDA / SCR offset calibration for MRI

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 Guidelines for recording  biopotential measurements in the MRI environment.

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