Gelfree electrode cap: impedance fluctuation
Poulami_Mandal
Mumbai,India
How did you measure sculp impedance in openBCI with gelfree electrode ? I mean when we press test button and release it shows some impedance around 15 kohm and when we go to another test button the impedance always increases to 60 to 70 kohm. I mean it fluctuates a lot.
When we press check all channel then the impedance updates in 5 seconds as in task bar it is set for 5 seconds but last impedance increases to 60 to 80 kohm always.I do not understand why it is happening?
Comments
Richard @retiutut, have you seen any such fluctuations in your testing?
With the new widget, is it possible to monitor impedance of a single channel 'continuously' to track the moment to moment changes?
William
If you are not moving or pressing on the cap when the impedance dramatically changes values, then this possibly sounds like some kind of glitch in the impedance widget. Mentioning Richard @retiutut.
The previous way to continuously monitor the per channel impedance, involved pressing the 'ohm' button on the time series channel display. It was later realized that measuring impedance on more than one channel at a time, could introduce cross-channel interference in the impedance. Thus the new widget just measures only one channel at a time.
But the behavior that Poulami describes, sounds like some kind of cross-channel effect is still happening?
William
@Poulami_Mandal, hi.
Can you update this newly created issue with the OS and GUI information? Thanks,
https://github.com/OpenBCI/OpenBCI_GUI/issues/1121
There is nothing here that seems like an obvious bug. I would need to see a video recording of what's happening. The values from the screenshot are likely correct. When checking impedance there is a small spike between 0-1 seconds that happens as a result of reconfiguring the ADS1299 and starting the data stream. This is why the auto-check-all-channels feature default is > 3 seconds to allow for the channel to stabilize.