ADS1299 + impedance + EDA simultaneously

Eohan George71

Other Parts Discussed in Thread: ADS1299, AFE4300

Hi,

I'm using an ADS1299 to record EEG. However, I would also like to measure the impedance(AC) and the electrodermal activity(EDA) simultaneously from the same electrodes. Is either of them supported by the chip ?

over 8 years ago

0 Brian Pisani over 8 years ago

TI__Mastermind 38745 points

Eohan,

Unfortunately the ADS1299 does not have this capability. This post has information about some TI designs to do body impedance and EDA (in the post it's called GSR) using the AFE4300.

Regards,

Brian Pisani

0 Eohan George71 over 8 years ago in reply to Brian Pisani

Prodigy 40 points

Hi Brian,

Thanks for the feedback. Is it possible to use the DC lead off detection to measure the body impedance between two electrodes? Page 31 on datasheet mentions that ADS1299 could do DC lead off detection simultaneously with EEG capture.

0 Brian Pisani over 8 years ago in reply to Eohan George71

TI__Mastermind 38745 points

Eohan,

It is generally not possible to do impedance measurement using dc lead-off detection. This is because the bias electrode will sink some of the lead-off current that would otherwise flow only between the two measurement electrodes. Alternatively, you could use ac lead-off detection with an ac coupled front end. Still, though, the measurement limitation comes in the accuracy of the current source. The accuracy is shown in the datasheet at +/-20%. It was really built for lead-off detection rather than impedance measurement.

Brian Pisani

0 Eohan George71 over 8 years ago in reply to Brian Pisani

Prodigy 40 points

Thanks for clarification Brian

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ADS1299 + impedance + EDA simultaneously