Design and implementation of EEG measuring system

Electroencephalographs (EEG) is a technique commonly used in medical and research fields to record the electrical activities of the brain. The EEG signals are recorded from the surface of the scalp using Ag/AgCl electrodes (locally made) according to the 10-20 international system. Measurements are usually difficult due to small signal magnitude and large DC offset. The signal is amplified in multistage amplifier and digitized using 24-bit analog to digital convertor (ADC). The DC-offset was treated using auto-zeroing technique, along with the use of high precision electronic components. The theoretical design was first simulated using TINA-TI software, then the PCB´s were designed using Eagle software, and implemented practically. EEG signals were acquired and recorded for different people and it seems satisfactory for the diagnosis by doctors.