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Lead off detection in the ADS1299 PDK

Heejin Kim
Intellectual 270 points
Other Parts Discussed in Thread: ADS1299

Hello

I am trying to use the lead off detection function with the ADS1299 PDK.

Before this, I confirmed that this kit could measure EEG properly.

But I am not sure whether I can test lead off detection function to measure the impedance of the individual electrodes.

On the kit, I will connect the (+) input connector to the (-) input connector, which is then jumped to the ground connector.

If the 6nA current is injected to the input wire, voltage drop across two connectors would appear, I think.

(In this case, about zero resistance would appear. Is it right?)

Could you give me some tips about setting up the register on the GUI?

Thanks ^^

  • 0
    TI__Mastermind 38745 points
    Hey Heejin,

    I would not go as far as to say you can measure impedance with lead-off detection since that implies that there is good measurement accuracy. The lead-off detection feature is only to be used as more or less a means to approximate rather than measure. The current sources are not nearly accurate enough for me to endorse it as a tool for measurement.

    However, if you are interested in making rough measurements, you are on the right track. The one thing I would potentially change is that I would not connect the inputs to ground if you are using unipolar supply mode since that is technically outside of the valid common mode input range for the device. I would recommend placing the common-mode somewhere closer to mid-supply if you can. If you are using bipolar supplies, then connecting them to ground is ok.

    Regards,
    Brian Pisani