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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
  • Hi Eoghan,

    today I changed on board RTIA on 2.2kohm, RLIMIT on 1kohm and RG on 47kohm.

    RCM1 and RCM2 are still 10Mohm and CISO1 - CISO4 are 47nF also.

    In application I changed RTIA on 2.2kohm and IN-AMP GAIN on 2.05.

    I used different frequencies like 500Hz, 1kHz, 10kHz, 25kHz, 50kHz......

    Also I tried to changed amplitude from 200mV to 600mV.

    I do not know.... the phase output is strange (but -154 is not good at all) and the magnitude is sometimes good and sometimes bad.

    If you have any idea what I am doing wrong, please help me.

    Thanks in advance

    Best regards

    Marian

Reply
  • Hi Eoghan,

    today I changed on board RTIA on 2.2kohm, RLIMIT on 1kohm and RG on 47kohm.

    RCM1 and RCM2 are still 10Mohm and CISO1 - CISO4 are 47nF also.

    In application I changed RTIA on 2.2kohm and IN-AMP GAIN on 2.05.

    I used different frequencies like 500Hz, 1kHz, 10kHz, 25kHz, 50kHz......

    Also I tried to changed amplitude from 200mV to 600mV.

    I do not know.... the phase output is strange (but -154 is not good at all) and the magnitude is sometimes good and sometimes bad.

    If you have any idea what I am doing wrong, please help me.

    Thanks in advance

    Best regards

    Marian

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