why the sample rate is not up 1000HZ?

I have a question, the ADS1299 can offer up 16KHZ sampling rate, why GUI only offer 1000HZ , whether you have plan to increase the sample rate on GUI?

Comments

  • wjcroftwjcroft Mount Shasta, CA

    Profeel, hi.

    Cyton's default sample rate is 250 Hz. This is a limitation imposed by the RFduino Bluetooth radio link. Using a Wifi Shield with Cyton will allow faster rates. But the Shield is currently on hold for Cyton, while some power supply mods are tested. It will be back in the Shop store later this year. However even with the Shield, there are limitations in terms of ESP8266 and Wifi data rates.

    To be realistic, most research EEG tops out at 500 or 1000 Hz. There is generally no need to go faster, as scalp EEG is greatly attenuated above 40 Hz gamma. In other words, increased sample rate above 500 or 1000 Hz, gets you NOTHING as far as increased resolution or information or signal quality.

    I've actually gone over this in past threads with you here on the forum.

    https://openbci.com/forum/index.php?p=/discussion/1642/cannot-get-500-or-1000-hz-sample-rate-from-wifi-shield-or-sd-card

    Etc.

    William

  • I am researching a special brain EEG, it is the sixthing feeling phenomenon. It like the psychological induction between the twin brother. When the phenomenon happen ,it must have a signal out from one people, and into other people's brain, what is signal, I think that it is cortex signal, cortex EEG. The cortex EEG can be 500HZ or higher. So I need the higher sample rate. The nervous excitation time is 0.5ms-2ms, so the sample rate need 4000HZ to 1000HZ. It is why I need the higher sample rate reason. My english is not good, I don't know whether you can understand my means. I have seen some very good detail on the 1-500HZ by cyton with WIFIshield, but it is not enough, so I hope you can offer 4000HZ sample rate or higher. Thank you so much.

  • wjcroftwjcroft Mount Shasta, CA

    You cannot record cortical EEG from the scalp. Requires removing scalp and bone to reach direct cortex surface. Can only be done by a neurosurgeon in a hospital. Scalp EEG stops not much higher than 40 Hz. Due to conduction losses of the bone and other tissues. Also there is considerable contamination of 40+ Hz EEG with EMG (muscle artifact) from scalp muscles. If you have ever looked at 40 Hz EEG amplitudes, they are very very low, only a few microvolts and lots of noise.

  • wjcroftwjcroft Mount Shasta, CA
    edited January 13

    https://www.frontiersin.org/articles/10.3389/fnhum.2013.00138/full
    "High-frequency brain activity and muscle artifacts in MEG/EEG: a review and recommendations"

  • Rathin63Rathin63 India
    edited January 13

    I am working on Brainstem Response Acquisition where the entire game is of 10 ms.

    I need at least 100 samples in 10 ms. Hence, at least 10 kHz is desirable.

    WiFi Shield claimed to support till 16kHz. Any idea/alternatives to acquired brainwaves at such a higher data rate?

    Thank you.

  • wjcroftwjcroft Mount Shasta, CA

    @Rathin63, hi.

    The actual Shop page snapshot from 2018 is here,

    https://web.archive.org/web/20180822092044/https://shop.openbci.com/collections/frontpage/products/wifi-shield?variant=44534009550
    https://github.com/OpenBCI/OpenBCI_WIFI

    It stated:

    On most Wireless networks, the WiFi Shield can stream well at 1000Hz with the Cyton and Daisy boards and at 1600Hz with the Ganglion board. With a high speed network switch, sample rates over 2000Hz are possible with a theoretical limit of 16000Hz for the Cyton, 8000Hz for the Cyton with Daisy shield, and 12800Hz for the Ganglion.

    So unfortunately the 'theoretical limit' mentioned is just that, not possible with actual wifi equipment. The practical achieved rates of around 1K to 2K are more in line with reality. The Wifi Shield will be back in the Shop later this year. It's undergoing some power supply circuit adjustments to better work with Cyton. It has always worked fine with Ganglion.

    It may be possible to sample at higher rates to the SD card, but here again, there are limitations involving SD card buffering and write speeds.

    More past Forum threads related to SD card sample rates here,

    https://www.google.com/search?q=sd+card+sample+rate+site:openbci.com

    Regards, William

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