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18 Monitoring EEG Using the EEG Impedance/Montage Window
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About Electrode-to-Skin Impedance
Electrode-to-skin impedance is the main quality indicator for the measured EEG signal. During
normal EEG monitoring, electrode-to-skin impedance is measured continuously and disconnected
electrodes are detected. The impedance value for each single, independent signal electrode is displayed
in the EEG Impedance/Montage window. If the measured electrode-to skin impedance of one or
more electrodes is above the limit, an INOP will be issued.
For impedance measurement at least two electrodes, plus the reference electrode, must be connected.
Impedance Indicators
Electrode/Skin Impedance Symbol Color Displayed
Impedance
Value
Action
Electrode not connected red no value connect electrode
Noisy signal gray 60 kΩ (fixed) check electrode-to-skin
connections
Electrode connected, impedance
above limit
yellow measured value
(e.g 15 kΩ)
check limit, check
electrode-to-skin contact
Electrode connected, impedance
at or below limit
green measured value
(e.g. 3 kΩ)
no action necessary