The wireless 8-channel electronencephalography (EEG) system enables ambulatory EEG monitoring. The system measures 8 EEG signals in a referential configuration, with the reference usually placed at the mastoid. The system relies on an ultra-low-power ASIC for the acquisition of the EEG signal, characterized by a high common mode rejection ratio (CMRR) (120dB) and low noise (60nV/sqrt(Hz)). The ASIC features an on-chip low-power ADC (11 bits), calibration and electrode impedance measurement nodes, and consumes only 200μW. In addition, the integrated EEG monitoring system includes a low-power microcontroller and radio providing local processing and wireless communication functionalities. The overall system consumes less than 10mW when sampling and streaming the data continuously at 1KHz. The system is integrated in a box of total size 50x30x10mm3, easily packaged in an elastic headband.
An important burden in remote and ambulatory EEG monitoring is the need to set up all the electrodes for an accurate recording. Many applications would benefit from an EEG headset that can easily be set up and worn by the user. In 2009, Holst Centre and imec have introduced a first prototype of EEG headset, attempting to provide an easy-to-set-up device for measuring EEG, see fig. 5. The headset consists of 10 electrodes in total, placed according to the International 10-20 standard. Commercial EL120 reusable electrodes are used, for their special contact posts designed for use through hair and fur. These electrodes are Ag/AgCl coated contact resistive electrodes. These electrodes are embedded into specially designed electrode housing, connecting the electrode to the headset, providing mechanical tilt, and ensuring signal transmission.