AFE4403: Possibility of implementation of wrist based SPO2 measurement system using AFE4403

Suresha N S

Part Number: AFE4403

Hi all,

We are prototyping a wearable in the form factor of Wrist watch & we need to integrate the SPO2 sensor to get SPO2 & Heart rate values.
Currently we have developed a prototype with standard off the shelf watch mechanical & used an alternate SPO2 sensor chip.
We are able to get the SPO2 & Heart rate values if there is no movement of the Hand on which the device is worn.

But whenever there is a movement of wrists, then we will get some invalid readings from the sensor.
We analyzed this issue further & below are the plots of raw photo-diode readings in both scenarios.

We think that the issue is related to the ambient Light variations & motion artifacts.

We would like to explore if there are any configurations / filters in AFE4403 to cancel out these noise ?
Please share if there are any specific technical papers from TI regarding this.

We are planning to move our solution to AFE4403 if these issues are addressed already.

We look forward to your valuable suggestions.

Thanks,
Suresha

over 7 years ago

0 Anand Udupa16 over 7 years ago

TI__Prodigy 215 points

Artefacts from Ambient light can be suppressed by doing a digital subtraction of the Ambient phase data (phase with LED off) from the LED phase data (phase with LED ON). The closer the spacing between the sampling instants, the better is this suppression.

Motion artefacts are much harder to address. SpO2 on wrist in the presence of motion artefacts would probably be a research topic in itself and there are no easy solutions to offer.

0 Suresha N S over 7 years ago in reply to Anand Udupa16

Expert 1070 points

Hi Anand,

Thanks a lot for the response.
Does AFE4403 has the ambient light supression algorithm built in itself or do we need to implement the algorithm on a controller or processor ?

Thanks,
Suresha

0 Anand Udupa16 over 7 years ago in reply to Suresha N S

TI__Prodigy 215 points

The ambient light suppression I am referring to is simply the digital subtraction of the Ambient phase data from the LED phase data. Since the ambient signal appears in both phases, it gets cancelled/ suppressed by the subtraction. The AFE4403 has a register from which you can directly read out the (LED-Ambient) value.

0 Suresha N S over 7 years ago in reply to Anand Udupa16

Expert 1070 points

Hi Anand,

Thanks a lot for your response.

Regards,
Suresha

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AFE4403: Possibility of implementation of wrist based SPO2 measurement system using AFE4403