ADS 1191: electrodes for differential ended mode?

Alexander Goldin

Expert 1220 points

What is suggested connection of electrodes for differential ended mode?

over 10 years ago

0 Brian Pisani over 10 years ago

TI__Mastermind 38745 points

Hey Alexander,

This ADC only converts signals differentially. If you have two electrodes, you should connect them to the IN1P and IN1N inputs. Do you have a patient drive electrode as well?

Regards,
Brian Pisani

0 Alexander Goldin over 10 years ago in reply to Brian Pisani

Expert 1220 points

Good day, Brian.

I sincerely glad to get your(!) answer.

We try to obtain and then process ECG signal using only two electrodes.

When we use three electrodes (one is reference), we do see results - signal/noise ratio is acceptable.

But when we use two electrodes, we simply cannot recognize proper signal - signal/noise ratio is poor.

What would you recommend?

0 Brian Pisani over 10 years ago in reply to Alexander Goldin

TI__Mastermind 38745 points

Hey Alexander,

If you only use two electrodes, you'll have to AC couple the inputs so that the input common mode does not drift. It's likely that your poor performance in the two electrode setup is due to drifts in the input common mode.

Regards,
Brian Pisani

0 Alexander Goldin over 10 years ago in reply to Brian Pisani

Expert 1220 points

Thank you, Brian. I will try it.

0 user4457532 over 10 years ago in reply to Brian Pisani

Prodigy 10 points

Hi Brian,

I am also interested in two electrodes ECG chest strap design.
I saw there is a demo video of chest strap HRM www.ti.com/.../support
However, I can not find related reference circuit.
Could you tell me where I can find it?

Thanks!
Scott

0 Ryan Andrews over 10 years ago in reply to user4457532

TI__Guru 66406 points

Hi Scott,

The chest strap demo you mention was never released for public purchase. However, the schematic and BOM files have been shared on this post:

e2e.ti.com/.../1296393

Regards,

Data converters

Data converters forum

ADS 1191: electrodes for differential ended mode?