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Ads1298r Respiration phase

Evert Dekker
Prodigy 140 points
Other Parts Discussed in Thread: ADS1298R

After reading Sbaa181.pdf  "Respiration Rate Measurement Based on Impedance Pneumography" it's still not clear to me when to use what value for the respiration phase register.
Playing around with the ADS1298R-EGG-FE demonstration kit it looks like how higher the phase shift is set how more noise there is. This will be because the gain is dropping if the modulated and demodulated signal are out of phase.
My patient simulator has no phase shift, what's the best way to add this?
What's the best value for the  Respiration phase register, or how determine the best value with a "real patient" ? Does this dependence on the patient his weight, bmi or.....?
What are normal values for "normal" people?

A lot of questions, maybe somebody can help us a bit to understand.

  • 0
    TI__Guru 66466 points

    Hello Evert, 

    Thanks for your post.

    You do not need to introduce the phase shift in the patient simulator. Instead, you can evaluate the different phase settings directly on the ADS1298R ECG-FE by changing the RESP_PHx bits in the RESP (16h) register. The ADS1298R can generate the modulation and demodulation signals internally based off of the internal clock.

    The relationship that you observed between phase shift and noise is correct. We offer a couple suggested Gain and Phase settings on page 79 of the datasheet for modulation clock frequencies of 32kHz and 64kHz.

    For example:

    I hope this helps!

    Best Regards,