Beginner question: 200hz vs 250hz and 'spatial resolution'

LokitoesLokitoes Australia
in Hardware
Hi all,

Sorry for starting out with these very beginner questions, and sorry if these have been answered before - I did a bit of searching but couldn't find what I'm looking for. 

I'm trying to decide whether to purchase a Ganglion or a Cyton for some home-made projects. When OpenBCI discuss the differences between the Ganglion and the Cyton, they mention two factors - a difference in hertz, and a difference in spatial resolution.

Q1: Am I right in assuming that 'spatial resolution' just means number of places being picked up on the body? How does this relate to ECG and EMG that usually just use 3 electrodes? What would be an example of an ECG or EMG set up requiring up to 8 pins? If, for example, it meant I could theoretically connect two people's EMG data to the same board, I'd be more than happy to go with the Cyton.

Q2: What does the difference in hertz mean in practice? Does it make a difference to the latency of the data coming through? Or does one pick up more noise? Or is this only important in EEG applications? (I'm not ready yet to dabble in EEG). I will be having to use bluetooth, not the wifi shield, so any improvements in latency that I can manage are important to me.

Thanks for any help you can give me.
- Lokitoes

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Lokitoes, hi.

    Generally 200 and 250 Hz sample rate is adequate for EEG, and certainly fine for ECG also. EMG at these rates can work ok, but note that typical EMG for clinical or research use might use higher rates like 500 or 1000 Hz. So for this you would need a Wifi Shield.


    Cyton can work with two subjects connected to the same board, as you suggest. Ganglion only has 4 channels.

    'Latency' is a different term than 'sample rate'. Latency is governed by delays in the radio communications, operating system latencies, etc. In general OpenBCI latencies work just fine with biofeedback protocols.

    Regards,

    William

  • LokitoesLokitoes Australia
    Thanks William! Very helpful. 
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