What is an acceptable impedance threshold for EEG electrodes to ensure good signal quality?

What is an acceptable impedance threshold for EEG electrodes to ensure good signal quality?

• A. Less than 5 kΩ
• B. Less than 20 kΩ
• C. Less than 50 Ω
• D. Less than 100 kΩ

Answer: (A)

Keeping EEG electrode impedance low is essential for a clean, reliable signal. The electrode-skin interface acts like a resistive path that also involves capacitive charging, so higher impedance means more susceptibility to noise, drift, and interference, and it can degrade the signal-to-noise ratio across channels. When impedance is kept under five kilo-ohms, the contacts are tight and stable enough to minimize these problems, providing clearer brainwave signals in the usual EEG frequency range. Values higher than this, such as several tens of kilo-ohms, tend to introduce more noise and make the data more variable over time and between channels, which can compromise the quality of sleep staging or diagnostic interpretation. Impedance that is unrealistically low (like 50 ohms) isn’t feasible with skin contact and standard gels. By properly preparing the skin and using appropriate conductive material, you can achieve and maintain this acceptable threshold for consistent signal quality.

Keeping EEG electrode impedance low is essential for a clean, reliable signal. The electrode-skin interface acts like a resistive path that also involves capacitive charging, so higher impedance means more susceptibility to noise, drift, and interference, and it can degrade the signal-to-noise ratio across channels. When impedance is kept under five kilo-ohms, the contacts are tight and stable enough to minimize these problems, providing clearer brainwave signals in the usual EEG frequency range.

Values higher than this, such as several tens of kilo-ohms, tend to introduce more noise and make the data more variable over time and between channels, which can compromise the quality of sleep staging or diagnostic interpretation. Impedance that is unrealistically low (like 50 ohms) isn’t feasible with skin contact and standard gels. By properly preparing the skin and using appropriate conductive material, you can achieve and maintain this acceptable threshold for consistent signal quality.