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ADS1299: EEG BIAS & REF Connection Question

Yenni Hsu
Prodigy 10 points
Part Number: ADS1299


Tool/software:

Hi all EEG experts, I would like to ask a few questions.

We only measured one channel of EEG signals.  

The ADS1299 FFT result is displayed below. 

 

However, we aim to lower the baseline noise level to around -140 dB because brainwave signal is not obvious. 

Is there any misconfiguration?  

Or is there any area where we can further improve?

If anyone could kindly provide an answer, I would be sincerely grateful.

The connection is as below,  

- Ch1 + : Connected to the scalp at the Cz position  

- Ch1 - : Connected to the earlobe  

Reference Connection:  

- Short-circuit Ch1- with the pin to its left  

- On JP25, pins 1–2 and 5–6 are also short-circuited  

- The two left pins on JP7 are shorted  

- The two right pins on JP8 are shorted  

 Bias Connection:

- JP1 pin2 is connected to the forehead  

And the ADS1299 Evaluation Software settings are as below,

 

  • 0
    TI__Guru 66816 points

    Hello Yenni,

    Thank you for your post. Please find the following feedback:

    1. If you are only using one channel, you can simplify the setup and connect the input electrodes directly to CH1+ and CH1- on the J6 header. You do not need to set any jumpers on JP25, JP7, or JP8. Also, you can open the SRB2 switch for CH1 in the GUI settings.
    2. If you want to use the SRBx pins to route the reference electrode, you must change the SRB2 setting to "Open" and change the SRB1 setting to "Closed." Currently, the reference electrode is routed to REF_ELEC through JP25 and buffered by U4. The output of this buffer is connected to the SRB1 pin. In this configuration, I recommend removing the jumper from J6[33-34] since IN1N will be open-circuit when SRB1 is used.

    The noise you are seeing is caused by power line interference at 60 Hz. Eventually, some of this noise may still be present after improving the setup. The remaining noise is typically filtered in software via low-pass or notch filter.

    Regards,

    Ryan

  • 0
    TI__Guru 66816 points

    Hi Yenni - Since we already have a direct email exchange about your application, please feel free to respond directly via email whenever you have follow-up questions.

    Regards,

    Ryan