Before recording, please verify that the EEG cap fits the head and that each electrode makes consistent contact with the scalp.

 
Begin by activating the impedance check in the acquisition software.


If all electrodes appear red or show high impedance, the first step is always to inspect and reapply the reference (CMS) and driven ground (DRL) electrodes. The recommendation is that they are set in the Mid Cranial Line


Poor contact or inadequate skin preparation at these two sites will cause the entire array to appear out of range.

Kendall electrodes:

  1. Clean the skin with alcohol, and then apply a small amount of mild abrasive paste (such as Nuprep or similar) to gently reduce surface resistance.
  2. Rub the paste for several seconds using a cotton swab or gauze pad to improve electrical contact.
  3. Wipe off any excess, then reapply conductive gel and ensure firm, even contact before rechecking the impedances.
  4. Correctly preparing the CMS and DRL electrodes in this way often restores all channels to normal impedance values.


Earclip (not the recommended option):

  1. Remove the ear clip and inspect the earlobe for proper placement.
  2. Clean the skin thoroughly with alcohol and then apply a small amount of mild abrasive paste (such as Nuprep or similar) to the area of contact on the earlobe.
  3. Gently rub the paste for several seconds using a cotton swab or gauze pad to reduce surface resistance and improve electrical connection.
  4. Wipe off any excess paste, apply a small amount of conductive gel to the ear clip sensor, and reattach it firmly to the prepared site.
  5. Make sure that the clip sits evenly and that both contact surfaces are touching the skin without pinching.



Once reference and ground are confirmed, address any persistently high-impedance electrodes individually.


The typical corrective sequence involves gently parting the hair to expose the scalp, applying additional conductive gel, and verifying that the electrode housing is seated firmly.

If impedances remain elevated, clean the skin with an alcohol swab then re-measure. In stubborn cases, light use of abrasive paste can further reduce skin resistance, though it should be applied sparingly to avoid discomfort or irritation. 


The best impedance values will be achieved 


If high impedances continue, please refer to: https://supportne.freshdesk.com/a/solutions/articles/35000289446