This demo will use EVAL-ADICUP3029, EVAL_AD5940BIOZ and Impedance-Test board to carry out EDA measurements.
This example project is designed to carry out electrodermal activity (EDA) measurements. The Impedance Test board is provided with the hardware which models skin impedance. It consists of a range of resistors and capacitors which can be used to model skin impedance, contact impedance and electrode impedance.
Alternatively, the custom cables can be connected to a human body simulator to measure actual body impedance. Note the cables must never be connected to the human body.
The following is a list of items required to carry out the measurement.
The AD5940 Z Test board is designed to model skin impedance, body impedance, electrode contact impedance and electrode impedance. There are 5 banks of switches on the board labelled S1, S2, S3, S4 and S5. For EDA application only S2 and S3 banks are applicable. The following tables indicate the resistor or capacitor value associated with each switch in bank 1 and bank 2. By default, all switches on S2 and S3 are in the ON position. No resistor or capacitor is connected to the measurement loop. Moving the switch to the Off position connects the corresponding resistor or capacitor value in series on the signal path. If more than one switch is closed the corresponding resistor values are connected in series. Typical impedance ranges for EDA measurements is 20kΩ up to 10MΩ. With this in mind the applicable switches are on S2 switch 6 to switch 12 and on S3 from switch 5 to switch 12.
|S2 Bank||Corresponding Res/Cap Value|
|S3 Bank||Corresponding Res/Cap Value|
The source code and include files for the project can be found on Git
To compile and run the example open the project in either Keil or IAR.
The measurement results are sent to the PC via UART. To establish connection over UART, connect the Micro-USB cable to the PC and to the EVAL-ADICUP3029 board. A terminal program such as RealTerm or Putty is required to display the results
Following is the UART configuration.
Select COM Port Baud rate: 230400 Data: 8 bit Parity: none Stop: 1 bit Flow Control: none
The data on the terminal consists of the Frequency of the excitation signal, the magnitude of the impedance and the phase of the impedance in degrees as in below screenshot.