Bioimpedance Measurement Using ADuCM350

Setup

Note this is an example "reference" to setup the ADuCM350 for 4-Wire Skin impedance measurements.

4-Wire measurements are for Absolute Accuracy and the ADuCM350 requires an external In-Amp.

For Relative measurements, the ADuCM350 can operate as a single chip solution.

Review AN-1302 for the differences between 2-Wire Skin Impedance and 4-Wire Skin Impedance. AN-1271 is useful to optimize the ADuCM350 Impedance engine for optimal performance.

• Documentation: AN-1302, and Configuring ADuCM350-BIO3Z board for 50kHz Bio-Impedance Measurement.pdf

• Hardware
  • Eval-ADuCM350EBZ (LK1 is in place)
  • ADuCM350 4Wire Bio Config 3 (Eval-ADuCM350BIO3Z) board. (LK7, LK8, LK9, LK10 in place; LK16, LK17, LK18, and LK19 in position B)

• Software
  • ImpedanceMeasurement_4WireBioIsolated_BodyComp example in IAR Embedded Workbench
• View data in Comms port / Terminal IO (Check SDK Userguide in document folder for details).

Note: When performing the Bio-Impedance measurement on the body, please ensure the laptop is unplugged from the power source as an additional precaution.

SDK Download /Debug and Collect Data

• Download and Debug Code
  • As Per SDK Quickstart UG-677
• In default mode 1.5KOhm is selected.
  • See 4-Wire Bio Config 3 schematic and layout.
• Theory / System connections  documented in detail on AN-1302 apps note
• Once Code is Download -> Run Code and view data in Terminal I/O or UART.
• Should get results below out of box for default settings.

Validate Results

• Hardware Change: Connect LK16, LK17, LK18, and LK19 in position A. insert USB-mini Cable, stripped at the other end, and connect the impedance to be measured at the stripped end.
• Repeat Measurement.
  • Hit Reset and then Run buttons
  • You should see impedance connected in the stripped end  of the USB-mini cable in results display.

Data View

The raw DFT complex results (real and imaginary parts) and the final calibrated unknown impedances (represented in polar coordinates; magnitude and phase) are reported through the UART/STDIO. The USE_UART_FOR_DATA macro determines whether the results are returned to the UART or STDIO.

To return data using the UART, set the macro USE_UART_FOR_DATA = 1 (this is the default option).

To return data using STDIO, set the macro USE_UART_FOR_DATA = 0.