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Using electrodes with ADuCM350 4 Wire BioZ board

Hi Eoghan,

I would like to ask you for advice.

I do not know if I am doing again something wrong.

Today I wanted to try measure with 4 electrodes system.

I found on the analog device site (4Wire-Isolated-Bioimpedance ADuCM350 Connections To Sensor), that when I want to measure with 4 electrodes I have to remove all links besides (LK7 - LK10) and all R_access resistors. So, I did this. I put the wires on that places and I connected the AD8226 as is pictured in pdf (http://www.analog.com/media/en/technical-documentation/application-notes/AN-1302.pdf - page 14 to 15).

The measured output is different that I expected. When I increase the frequency the impedance is increasing. And I also tried to measure the output from AFE8 with oscilloscope and I am not able to measure anything. Maybe the measured impedance is therefore wrong because there is no output or lots of noise.

Thanks in advance

Best regards

Marian

Parents
  • OK, I tried to measure with 2-wire mode.

    I attached output from simulation and also the circuit that I measured.

    And here are the output from ADuCM350. I used EKSP SW.

                                                                          

    Amp =   600mV kHz Mag Phs
    Rcal = 1000 ohm 10 2175 -30,54
    Rtia = 2200 ohm 20 1684 -30,86
    30 1408 -31,447
    40 1249 -32,29
    50 1156 -33,619
    60 1082 -35,866
    70 1027 -38,4
    80 1055 -23,2

                                                                          

    Amp =   600mV kHz Mag Phs
    Rcal = 1 kohm 10 2175 -30.54
    Rtia = 2.2 kohm 20 1684 -30.86
    30 1408 -31.447
    40 1249 -32.29
    50 1156 -33.619
    60 1082 -35.866
    70 1027 -38.4
    80 1055 -23.2
Reply
  • OK, I tried to measure with 2-wire mode.

    I attached output from simulation and also the circuit that I measured.

    And here are the output from ADuCM350. I used EKSP SW.

                                                                          

    Amp =   600mV kHz Mag Phs
    Rcal = 1000 ohm 10 2175 -30,54
    Rtia = 2200 ohm 20 1684 -30,86
    30 1408 -31,447
    40 1249 -32,29
    50 1156 -33,619
    60 1082 -35,866
    70 1027 -38,4
    80 1055 -23,2

                                                                          

    Amp =   600mV kHz Mag Phs
    Rcal = 1 kohm 10 2175 -30.54
    Rtia = 2.2 kohm 20 1684 -30.86
    30 1408 -31.447
    40 1249 -32.29
    50 1156 -33.619
    60 1082 -35.866
    70 1027 -38.4
    80 1055 -23.2
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