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ADS1291: Can the positive and negative electrodes of each channel be captured on two different battery powered devices and then be combined after in post processing software?

Part Number: ADS1291

Tool/software:

This may be a confusion question.

lets say i have two ADS1291 devices. they are localized to two different parts of the body ( left arm /  right arm).

is it psosible to obtain the raw signal from each and then (assuming you could synchronize them to a high degree of accuracy,) combine the signals through differential amplification after the fact, once digitized and processed by a computer.

I notice when i use one electrode, the other electrode reports lead off and then i see zero activity on the data stream.

  • Hi Kyle, 

    Yes, that was a confusing question. Slight smile Can you try to rephrase?

    Regards,

    Ryan

  • my understanding of the ADS system is that it is a differential amplifier,  amplifying the difference between two electrodes, and eliminating common noise.  it does this on chip.   

    is it possible to sample just one electrode, noise and all?       with the purpose of doing the differential amplification after the signal is digitized?

    There is one unique use case that would rely on this being possible. I dont want to get too into the weeds of "why" just is it possible to obtain the same data  assuming the two data streams were synchronized in time?

  • Hi Kyle,

    Thanks for the explanation. Yes, it is possible to measure just one electrode. However, each channel is always measuring and converting the voltage potential between two input pins (INxP and INxN); therefore, you would have to connect the unused input to some common-mode potential. I would recommend mid-supply as this would closely match the common-mode voltage of the electrode inputs in a system using RLD and minimize the channel offset at the PGA input. The offset can be removed in post-processing anyway, but the point of minimizing it in analog is to allow the most PGA gain. Do you plan to have an RLD electrode in your system to bias the body?

    Regarding the synchronization requirement, if you connect one electrode to CH1 and a second electrode to CH2 (i.e. IN1P and IN2P), then the two channels would be simultaneously sampled.

    Regards,

    Ryan

  • wonderful info thank you,  I had a feeling this was possible. that makes sense.

    Yes I have RLD avaliable.