ABSTRACT
This chapter describes the electrodes and amplifiers used to record bioelectric potentials, and the sources of the potentials. It analyses sources of noise and low-noise amplifier design. The chapter also describes special medical isolation amplifiers. It covers the recording of the very small, transient magnetic fields resulting from the transient flow of ionic currents accompanying nerve and muscle action potentials. The chapter introduces super-conducting quantum interference device (SQUID) and shows how it is used to monitor brain and heart electrical activity, and so on. The noninvasive (NI) measurement of bioelectric potentials from the body surface generally makes use of electrochemical electrodes to couple the electrical potentials at points on the skin surface to the copper wires that connect to the signal-conditioning amplifier/recorder. Two different electrodes coupled by a common electrolyte form an electrochemical cell. The chapter examines the systems properties of biopotential amplifiers while giving minimum attention to the electronic circuit details of their innards.
