Title: Capacitive driven-right-leg circuit design

Authors: Marcelo Alejandro Haberman; Enrique Mario Spinelli; Pablo Andrés García; Federico Nicolás Guerrero

Addresses: Industrial Electronics, Control and Instrumentation Laboratory (LEICI), Engineering Department, La Plata National University, CC 91 - (1900) La Plata, Argentina ' Industrial Electronics, Control and Instrumentation Laboratory (LEICI), Engineering Department, La Plata National University, CC 91 - (1900) La Plata, Argentina ' Industrial Electronics, Control and Instrumentation Laboratory (LEICI), Engineering Department, La Plata National University, CC 91 - (1900) La Plata, Argentina ' Industrial Electronics, Control and Instrumentation Laboratory (LEICI), Engineering Department, La Plata National University, CC 91 - (1900) La Plata, Argentina

Abstract: Capacitive electrodes allow to pick-up biopotentials through a dielectric layer, without using electrolytes. However, this technique is vulnerable to electric-field interference, mainly to common mode voltages produced by the 50 Hz power-line. A fully Capacitive Driven Right Leg (CDRL) circuit is proposed to reduce the patient common mode voltage v_CM. The design of this circuit takes into account several factors as electrode impedance, stray coupling capacitances and amplifier transfer function response. All these parameters are addressed to ensure the circuit's stability in most biopotential acquisition scenarios. Monte Carlo analyses were performed to find the worst conditions, resulting in a maximum CDRL gain between 70 and 80 dB. The CDRL was implemented as an independent block that can be used for different applications such as ECG, EMG or EEG. Several experimental results are presented, showing good quality recordings even using SE amplifiers, an appropriate approach for multichannel acquisition systems.

Keywords: capacitive electrodes; insulating electrodes; common-mode interference; right-leg circuits; non-contact measurements; electromagnetic interference; EMI; biopotential signal acquisition; biomedical engineering; patient common mode voltage; circuit design; electrode impedance; stray coupling capacitances; amplifier transfer function response; Monte Carlo simulation.

DOI: 10.1504/IJBET.2015.068051

International Journal of Biomedical Engineering and Technology, 2015 Vol.17 No.2, pp.115 - 126

Received: 19 Jul 2014
Accepted: 02 Oct 2014
Published online: 15 Mar 2015 *

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