INVESTIGADORES
HABERMAN Marcelo Alejandro
artículos
Título:
Insulating electrodes: a review on biopotential front ends for dielectric skinelectrode interfaces
Autor/es:
ENRIQUE SPINELLI; MARCELO HABERMAN
Revista:
PHYSIOLOGICAL MEASUREMENT
Editorial:
IOP PUBLISHING LTD
Referencias:
Año: 2010 vol. 30 p. 183 - 199
ISSN:
0967-3334
Resumen:
Insulating electrodes, also known as capacitive electrodes, allow acquiring
biopotentials without galvanic contact with the body. They operate with
displacement currents instead of real charge currents, and the electrolytic
electrodeskin interface is replaced by a dielectric film. The use of insulating
electrodes is not the end of electrode interface problems but the beginning of
new ones: coupling capacitances are of the order of pF calling for ultra-high
input impedance amplifiers and careful biasing, guarding and shielding
techniques. In this work, the general requirements of front ends for capacitive
electrodes are presented and the different contributions to the overall noise
are discussed and estimated. This analysis yields that noise bounds depend
on features of the available devices as current and voltage noise, but the final
noise level also depends on parasitic capacitances, requiring a careful shield
and printed circuit design. When the dielectric layer is placed on the skin, the
present-day amplifiers allow achieving noise levels similar to those provided
by wet electrodes. Furthermore, capacitive electrode technology allows
acquiring high quality ECG signals through thin clothes. A prototype front end
for capacitive electrodes was built and tested. ECG signals were acquired with
these electrodes in direct contact with the skin and also through cotton clothes
350 μm thick. They were compared with simultaneously acquired signals by
means of wet electrodes and no significant differences were observed between
both output signals.