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Problem in an ECG circuit

  1. Aug 14, 2015 #1
    Hello, I am trying to make a simple ecg/emg acquisition circuit.

    I am using 2 of these https://www.olimex.com/Products/EEG/Electrodes/EEG-AE/ active electrodes for the differential signal and this https://www.olimex.com/Products/EEG/Electrodes/EEG-PE/ as a passive DRL electrode.

    My supply is the 5V output of a LM7805 and I create a virtual ground at 2.5V using the TLE2426.
    This is what I have built in a breadborad.
    I connect the output of the INA118 to an oscilloscope but nothing usefull is shown.

    Do you see anything wrong in it?
  2. jcsd
  3. Aug 15, 2015 #2


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    Sorry --- deleted my post after you replied. LOL

    Actually, You are using it with a single supply in a weird way. I have no idea what will happen or what you are doing wrong. Sorry.
  4. Aug 15, 2015 #3
    I am using a theoretical ground at 2.5V so that we have a positive voltage supply +2.5V and a negative -2.5V.
  5. Aug 15, 2015 #4


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    It's specified for + and - 15V, so I expect 2.5V is far too little.

    I understand virtual ground. It's the subtleties of the electrode circuit I can't visualize. For example their Fig 9 shows gain to the RL electrode. I don't know enough about the signals to understand what your circuit might see differently.
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