How to Extract Electrode Impedance Values with UNIX Timestamps?
statius9
US
in Electrodes
I need guidance on extracting impedance values with corresponding UNIX timestamps. What methods or tools should I use to ensure both data points are captured accurately? Any help would be appreciated! For instance, is there a wiki, documentation, or another discussion post I can refer to.
Comments
Nicholas, hi.
There is no continuous-mode steam of impedance values during the data collection. Which board are you using?
Impedance is only available using the corresponding GUI widget, BEFORE you start the data collection.
https://docs.openbci.com/Software/OpenBCISoftware/GUIWidgets/#cyton-signal-widget
https://docs.openbci.com/Software/OpenBCISoftware/GUIWidgets/#ganglion-signal-check
William
Hi William,
Thank you for the response. I am using the Cyton Biosensing Board (8-channels).
Nicholas
Source code is here:
https://github.com/OpenBCI/OpenBCI_GUI/blob/master/OpenBCI_GUI/W_CytonImpedance.pde
Great! Thank you! It looks like I could modify this code to enable the headset to periodically check and store impedance values
But note, if you have used that widget, it cannot run simultaneously with the data collection. It takes over the board interface because it puts the ADS1299 into the special current injection mode.
Would you happen to know how long it would take to gather impedance values before we can resume recording EEG data? I'll of course dig into the details of the code: I imagine this can already be inferred from the code and that it would depend on the number of electrodes.
If you watch the impedance values while it is running, you can see that it updates one channel at a time. So you can gauge how long it takes to step through all channels. It just keeps cycling, so after one or two cycles should be stabile.
We are currently doing this in the Galea GUI, which is being distributed to Galea customers only at this time. It looks like this is a feature that could be easily included in the next Public GUI.
The OpenBCI Software team is planning to return to normal development schedule on non-Galea products before the end of this calendar year. We could see Galea v6.0.0 in the next few months. Currently, it is in Beta.
@retiutut Are you saying that in the Galea GUI we can export impedance values, e.g., to a CSV or some other data structure? Or are you saying that with the Galea GUI we can periodically check impedance values and export them continuously?
Do you plan to incorporate these features into the public GUI?
Impedance check is still done using injected current, so it's similar to Cyton check. It's not continuous. I just added the ability to export all of this data to file. Of course, if you left impedance check on it would still rotate through the channels indefinitely.