impedance values vary too much (Cyton and 2019 Gui)

mkarn3yru · March 2019

How do I measure the impedance from one channel with the open bci gui?

The values, when I click the impedance button, vary to much to be of any use.

Anyone has other ways of measuring the electrode-skin impedance?

Regards

wjcroft · March 2019

MKarn, hi.

What electrodes are you using? With some type of electrolyte (gel or paste), your impedance readings should be relative constant. The dry electrodes (combs, cones, or flat), are expected to vary more, because skin pressure is more a factor.

Can you just 'visually' take an average value by watching the upper / lower limits of the impedance numbers you are seeing? :-)

There are dedicated electrode impedance meters, such as,

https://www.google.com/search?q=eeg+electrode+impedance+meter

With modern EEG amps having high amplifier input impedance (Cyton is 1 gigaohm), actual skin electrode impedance is not much of an issue,

http://openbci.com/forum/index.php?p=/discussion/1471/what-impedances-are-to-expect-using-the-standard-dry-electrodes

Regards,

William

mkarn3yru · March 2019

the issue, with the latest release of the GUI in MAC OS is that the values vary for like 3 seconds and then go to zero

wjcroft · March 2019

OK, I wish you had been more explicit about the impedance number ramping down to zero, in your first post.

This issue was supposedly fixed recently, see this Github link,

https://github.com/OpenBCI/OpenBCI_GUI/issues/427

Can you mention what version of GUI you are running? Can you try another GUI version?

Mentioning @retiutut @produceconsumerobot

Regards,

William

mkarn3yru · March 2019

using V4.0.3 of OpenBCI_GUI

tried using the previous versions but they freeze in macOS Mojave v10.14.3

wjcroft · March 2019

Please pickup a later release here,

https://github.com/OpenBCI/OpenBCI_GUI/releases

I'm sorry that the Download page is still pointing to 4.0.3

I suggest 4.1.0 or 4.0.4

Apologies to @retiutut and @produceconsumerobot. However... I think Conor is now asking our web team to have auto updates of the Download page. Coming soon.

mkarn3yru · March 2019

Thanks a lot for the help!

will try that

impedance values vary too much (Cyton and 2019 Gui)

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