Medical Electronics Symposium Conference Proceedings


IMPROVING SIGNAL QUALITY AND TEST RELIABILITY IN EEG MEASUREMENTS USING INTEGRATED HIGH-DENSITY SURFACE-MOUNT ELECTRONICS

Author: Benjamin A. Schnitz et al.
Company: MicroNova Technology, Inc.
Date Published: 5/19/2004   Conference: Medical Electronics Symposium


Abstract: Electroencephalogram (EEG) measurements are often difficult to acquire due to the small signal magnitude. In particular, Evoked Response Potentials (ERPs) are typically in the range of 0.5 to 20 µV. Two of the biggest factors in transduction of EEGs and ERPs are electrode-skin impedance, which can often be many hundreds of k., and noise interference from long electrode lead-wires.

Typical solutions have been to decrease electrode-skin impedance by abrasion of the skin to remove the stratum corneum and by using electrolytes; to use instrumentation amplifiers with high (109 . or greater) input impedance to decrease the effects of high electrode-skin impedance; and to place an amplification point closer to the electrodes before running long lead wires to a computer or other data collection / visualization center.

Advances in surfacemount electronics in recent years have allowed greater accuracy in EEG and ERP measurements. In this paper we present design techniques which improve the signal quality and reliability in EEG measurements: by designing signal amplification and processing electronics into the electrode cap using modern surface-mount (SMT) packages, many of the previously described problems are eliminated.

SMT devices allow for high-order active filters roughly the same size of the electrodes themselves which can be placed on or near the electrode. Furthermore, SMT A/D converters may be place on the electrode cap. By sending digital, CMOS/TTL level signals across the lead wires rather than microvolt level analog signals, the effects of lead wire interference are completely removed.

Key words: electroencephalograms, biopotential measurements, surface-mount electronics.



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