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Instrumentation amplifier ECG sensing with opa2369 50Hz problem.

Uri Volansky
Prodigy 10 points
Other Parts Discussed in Thread: OPA2369

Hello .

I'm building an ECG amplifier.

I'm working with the OPA2369 because its a very low power consumer.

The power comes from battery and i use floating equipment to measure the output. 

It works great on my body , two inputs: one from  the chest (sternum) ,the other from the upper side ribs and an RLD below them.

For your knowledge without the RLD every movement of the muscles ruins the signal but with it, it works perfect.

my problem is  when i touch my grounded lab table, the signal is lost in a 50Hz sin pick to pick. 

I've added some RC filters on the inputs and on the feedback but nothing works!

please advice !?! 

  • 0
    TI__Mastermind 25795 points
    Hello Uri,

    We often get questions about ECG. Therefore we created a FAQ page about acquiring biomedical signals. Here is the link:

    e2e.ti.com/.../2437.ecg-heart-signal-acquisition.aspx

    I recommend starting with the "Design Considerations for ECG Systems" presentation.

    One additional recommendation is to try adding a capacitor across the inputs to filter the differential signal, which is shown on page 22 of the presentation. Please make sure the differential capacitor has at least 10 times the capacitance of the common-mode capacitors.