ADS1298: Seems to be "malfunction" appear when electrodes becom detached

Takumi Suzuki1

Part Number: ADS1298

Tool/software:

Hi,

Let me ask you your support about the phenomenon seems to be "malfunction" as below.

- When measuring an ECG using ch1 and ch4 of the ADS1298, an R wave appears in the ch1 output when the ch1+ electrode becomes detached.

- The amplitude of the R wave is small, but it is large enough to cause a doctor to misdiagnose the condition.

- This phenomenon does not occur with conventional ECG amplifiers (composed of an op amp and an instrumentation amplifier).

I suppose it is also likely that the problem is due to the internal circuitry(peobably MUX) of the AD1298.

Will you tell me your idea about this kind of phenomenon?

As I attached the register setting values, please check it.

And if possible, I would like the detailed block diagram of "MUX".

Thank you for your great support.

Best Regards,ADS1298 register setting Jan7 2025.xlsx

Takumi

11 months ago

0 Shane Aspenwall 11 months ago

TI__Prodigy 740 points

Hi Takumi,

Thanks for reaching out on the forum! As Ryan is currently out of office, expect a delay is response.

Regards,

Shane

0 Takumi Suzuki1 11 months ago in reply to Shane Aspenwall

Mastermind 8610 points

Hi Shane-san,

Thank you for your reply.

I see, let me wait for Ryan-san's reply.

Regards,

Takumi

0 Takumi Suzuki1 10 months ago in reply to Takumi Suzuki1

Mastermind 8610 points

Hi,

How about the situation?

I am looking forward to getting your support.

Regards,

Takumi

+1 Ryan Andrews 10 months ago in reply to Takumi Suzuki1

TI__Guru 67096 points

Hello Suzuki-san,

Thank you for your patience while I was out of the office.

It is possible for the output of the ADC channel to show an ECG waveform when only one electrode is disconnected. Do you notice the DC level of the channel output shifting when one electrode is disconnected? Depending on the common-mode of each input pin, it's possible to see a small AC signal on top of a large DC common-mode voltage when only one electrode becomes disconnected. To me, this does not indicate an issue with the device. Instead, the firmware should monitor the lead-off status for each input and disregard the channel data when one or both electrodes are disconnected.

Figures 25 and 29 of the device data sheet detail the internal MUX and PGA circuitry.

Regards,

Ryan

0 Takumi Suzuki1 10 months ago in reply to Ryan Andrews

Mastermind 8610 points

Hi Ryan-san,

Thank you so much for your reply !

I understoode.

Regards,

Takumi

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ADS1298: Seems to be "malfunction" appear when electrodes becom detached