Thesis - Instituto de Telecomunicações

3.4. MATERIALS AND METHODS 55Figure 3.12: Synchronization diagram. The electronic circuit in the middle enables thesynchronization of the mouse, webcam and acquisition system.which the described electrical modification was performed.BVPThe blood volume pressure sensor was placed in the distal phalange of the ring finger onthe non-dominant hand. The sensor was placed in the finger supported by two small elasticbands. The sensor was adjusted until a signal appears with qualitative high amplitude(i.e. we adjust the position until we obtain a signal where the heart beat cycle is clearlynoticeable in the monitor screen). Figure B.7 presents the sensor coupled to the hand inthe ring finger.ECGWe used a one lead ECG montage at the V2 derivation, to detect the subject heart beat.We placed a triode electrode, with standard 2 cm spacing of Ag/AgCl contacts, in the 4thintercostal space in the mid clavicular line. The positioning place was prepared by cleaningwith alcohol and conductive paste was used in the electrodes for improved signal quality.A strap was used to hold the electrodes in the defined position.