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This version (01 Mar 2019 17:11) was approved by Micheál Lambe.

Table of Contents

AD5940_EDA

This demo will use EVAL-ADICUP3029, EVAL_AD5940BIOZ and Impedance-Test board to carry out EDA measurements.

Overview

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.

Measurement Requirements

The following is a list of items required to carry out the measurement.

  • Hardware
    • EVAL-ADICUP3029
    • EVAL-AD5940BIOZ
    • Z-Test Board
    • Mirco USB to USB cable
    • PC or Laptop with a USB port
    • Custom Cables (Optional)
  • Software
    • AD5940_EDA Example Project (Git Lab)
    • Serial Terminal Program, Such as Putty or RealTerm
    • IDE such as IAR or Keil

Setting up the Hardware

  1. Set switch S2 to USB Arduino function in order to view data over UART. The UART baud rate is 230400
  2. Set S5 to Wall/USB to power the board from the USB cable
  3. Place the EVAL-AD5940BIOZ on top of the EVAL-ADICUP3029.
  4. Connect the AD5940 Z Test board to the EVAL-AD5940BIOZ board
  5. All jumpers should be in their default position
  6. Plug in the micro USB cable into the (P10) USB port on the EVAL-ADICUP3029, and the other end into the PC or laptop.

AD5940 Z Test Board

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
S1 100 Ω
S2 200 Ω
S3 300 Ω
S4 402 Ω
S5 10 kΩ
S6 23.7 kΩ
S7 42.2 kΩ
S8 42.2 kΩ
S9 100 kΩ
S10 200 kΩ
S11 1000 pF
S12 0.01 μF
S3 Bank Corresponding Res/Cap Value
S1 100 Ω
S2 200 Ω
S3 300 Ω
S4 402 Ω
S5 4.22 MΩ
S6 4.22 MΩ
S7 1.43 MΩ
S8 1 MΩ
S9 300 kΩ
S10 300 kΩ
S11 1000 pF
S12 0.01 μF

Obtaining the Source Code

The source code and include files for the project can be found on Git

AD5940 Source Code

Configuring the Software

To compile and run the example open the project in either Keil or IAR.

Outputting Data

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.

resources/eval/user-guides/eval-ad5940/software_examples/ad5940_eda.txt · Last modified: 01 Mar 2019 15:40 by Micheál Lambe

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