Single-unit EEG sensors contain multiple closely spaced dry electrodes that can hook onto skin and associated electronic circuitry such as amplifiers, A/D convertors, wireless transmitters, and a power source such as a battery. The electrodes can be separated by about 20 mm or less, and the associated circuitry can be situated within a volume defined by the multiple electrodes. The single-unit sensors hook onto the skin using a tooth surface so that a rotation of the sensor secures and electrically connects the sensor to the skin.
