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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.

Comments
Anonymous
  • Hi all,
    I have read the 313.attachment.pdf of BIO3Z board, and I have some question about it.
    On page 2of6 there is an example of the Impedance Parameters calculation.
    We would like to use the board at different frequences and we have to know which is the current in Zunknown.
    First of all we have to know:
    Which is the Rlimit value? Can we identify it on the board?
    Can you confirm that Zaccess1 and Zaccess2 are identify by the ones indicated in pag2of6 Access Impedance (Zaccess1=Rlimit+Ciso1; Zaccess2=Ciso2 with Ciso1/2=47nF)?

    Thank u all for your informations.
    Waiting for your news, Best regard

    Enrico De Tito

  • Hi all,
    I have read the 313.attachment.pdf of BIO3Z board, and I have some question about it.
    On page 2of6 there is an example of the Impedance Parameters calculation.
    We would like to use the board at different frequences and we have to know which is the current in Zunknown.

    First of all we have to know:
    Which is the Rlimit value? Can we identify it on the board?

    Can you confirm us that Zaccess1 and Zaccess2 are identify by the ones indicated in pag2of6 Access Impedance (Zaccess1=Rlimit+Ciso1; Zaccess2=Ciso2 with Ciso1/2=47nF)?

    Thank u all for your informations.
    Waiting for your news, Best regard
    Enrico De Tito

    •  Analog Employees 
    in reply to tariq

    Hi,

    The ADuCM350 offers far superior performance in accuracy and system usability.

    -Mark

  • greetings ...

    we are doing a project which is impedance cardiography, and we want to choose an impedance analyzer chip, but we are lost between ad5933 and aduCM350, which one is better ?

    thanks...

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