A capacitive electrode with fast recovery feature

ENRIQUE SPINELLI; MARCELO HABERMAN; PABLO GARCÍA; FEDERICO GUERRERO

PHYSIOLOGICAL MEASUREMENT

IOP PUBLISHING LTD

Lugar: Londres; Año: 2012 vol. 33 p. 1277 - 1288

0967-3334

Capacitive electrodes (CEs) allow for acquiring biopotentials without galvaniccontact, avoiding skin preparation and the use of electrolytic gel. The signalquality provided by present CEs is similar to that of standard wet electrodes,but they are more sensitive to electrostatic charge interference and motionartifacts, mainly when biopotentials are picked up through clothing andcoupling capacitances are reduced to tens of picofarads.When artifacts are largeenough to saturate the preamplifier, several seconds (up to tens) are needed torecover a proper baseline level, and during this period biopotential signals areirremediably lost. To reduce this problem, a CE that includes a fast-recovery(FR) circuit is proposed. It works directly on the coupling capacitor, recoveringthe amplifier from saturation while preserving ultra-high input impedance,as a CE requires. A prototype was built and tested acquiring ECG signals.Several experimental data are presented, which show that the proposed circuitsignificantly reduces record segment losses due to amplifier saturation whenworking in real environments.