Multiple Reading Set-Up (ECG and EEG)
Hey,
I want to simultaneously record ECG (standard 3-lead placement) and EEG data. If possible the data streams/signals should be independent / not influence each other! I read the tutorial for multiple ExG recording but unfortunately I don't have a Daisy Board.
My question now is, if I connect the ECG-ground-lead to bottom AGND pin of Cyton and the 2 reference pins for EEG to bottom BIAS and SRB2 pin, do I get accurate and independent ECG + EEG recordings?
Thanks in advance for any help 
Cheers,
destro
Comments
Have you read this article?
https://docs.openbci.com/GettingStarted/Biosensing-Setups/ExGSetup/
re: "I don't have a Daisy board"
The description at the link SHOWS Daisy, but does not depend on it. Just use the available 8 channels you have.
NO wires should connect to AGND. Your ECG channel should use the plus and minus pins on that channel. And NO Bias connection. Bias on Cyton (ADS1299) is the SAME AS Ground on other amps. So your EEG Bias connection on the head already provides 'Ground' for the ECG. No ECG "Driven Right Leg" DRL, is needed. Be sure to turn off SRB and Bias for the ECG channel in the settings.
Hey wjcroft, thanks for your fast reply
Yes, I read this article and also some other discussions in the forum and was confused about AGND (they use it in the tutorial but I keep reading it actually shouldn't be used at all for the Cyton), but I don't want to record EMG anyways. Another question, how can the EEG Bias provide ground for the ECG channel if I switch BIAS off for the ECG channel?
My use case is the following, I want to investigate if an ECG Signal can be robustly extracted from (around the ear) EEG by means of Independent Component Analysis. For the evaluation I need a reference ECG as "ground truth". That's why I want to record both standard lead ECG and EEG at the same time (independently from each other). Now with the configuration you described, the ECG recording is truly not influencing the EEG signals (and the other way round)?
Usually on biopotential amps such as the ADS1299, 'Ground' provides the function of 'centering' the differential amplifiers so that plus and minus diversions do not exceed the range required for accuracy. On ADS1299 'Bias' does BOTH this centering action (for all channels, regardless of Bias value in settings), AND Bias also injects a counter-mains very small signal to offset the very strong distortion coming in via EMF coupling to mains voltages. This injection is more important for the EEG channels due to their microvolt sensitivity.
Actual clinical ECG machines use 'DRL' for this same injection. But in your mixed signal case EEG needs the injection much more than the ECG.
William