Bioimpedance Measurement Using ADuCM350

Document created by LiamR Employee on Apr 24, 2014Last modified by emoloney on May 27, 2016
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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


  • Hardware
    • Eval-ADuCM350EBZ (LK1 is in place)
    • ADuCM350 4Wire Bio Config 2 (Eval-ADuCM350BIOZ) board. (LK7, LK8, LK9, LK10, LK16, LK17, LK21 in place)


  • Software
    • ImpedanceMeasurement_4WireBioIsolated example in IAR Embedded Workbench
  • View data in Comms port / Terminal IO (Check SDK Userguide in document folder for details).


SDK Download /Debug and Collect Data


  • Download and Debug Code
    • As Per SDK Quickstart UG-677
  • In default mode 20KOhm+ 220pF || 100KOhm is selected.
    • See 4-Wire Bio Config 2 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: Remove LK17 and LK21. Insert LK19.
    • Sensor now only the 20KOhm load.
  • Repeat Measurement.
    • Hit Reset and then Run buttons
    • You should see 20KOhm 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.