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ADS1293: Lead-off detection

Alwyn DSouza
Intellectual 360 points

Part Number: ADS1293
Other Parts Discussed in Thread: ADS1298, ADS1294, ADS1292

I intend using the ADS1293, however while looking through the forums I discovered this thread

I'd like to highlight a comment here, especially Brian's

"Apparently this device has issues measuring data when the contact impedance between the electrodes and the patient is very high. This can be especially troublesome when using dry electrodes."


I'd like to know if the lead-off detection of the ADS1293 has any issues like the one mentioned in Brian's comment, is there any workaround for this.

I'd really like to use the lead-off detection feature so any information on this would be useful.

  • 0
    TI__Guru 60022 points

    Hi Alwyn,

    The linked thread is about the ADS1293. Using wet electrodes and/or using sandpaper to scrape the skin can allow for a lower contact impedance electrode connection. 

  • 0 in reply to Alexander Smith
    Intellectual 360 points

    Hi Alexander,

    In general the ADS1293 lead-off detection still works but has issues when the electrode-skin impedance is beyond a particular threshold.? Is this correct?

    I need to know if this issue is only relevant to the ADS1293 or in general ADS1292, ADS1294 and ADS1298 all will face similar problems?

  • 0 in reply to Alwyn DSouza
    Intellectual 360 points

    Hi,

    Just trying to bump this thread up as no replies were received to my last question. If any TI expert can clarify if this problem only plagues the ADS1293 then it would help me select another chip like the ADS1294.

    TIA

  • 0 in reply to Alwyn DSouza
    TI__Guru 60022 points

    Hi Alwyn,

    Sorry for the delay in response, it was the weekend. 

    Any lead-off detection system will have issues when the electrode contact impedance is too high - the extreme being when the electrode is completely disconnected. The main thing to look at here is the excitation current - the ADS1293 supports 8nA up to 2040nA whereas the ADS1298 supports 6, 12, 18, 24nA excitation currents. Using the highest possible lead-off current while not violating the patient protection specifications is recommended.