ABSTRACT
This chapter addresses the problem of gaining access to physiological parameters. It considers how a physiological parameter is converted into an electrical signal which can be recorded and displayed. A complete measurement system consists of a transducer, followed by some type of signal processing and then a data recorder. Polarization is the result of direct current passing through the electrodes and it results in an effect like that of charging a battery, that is, the electrode potential changes. One of the problems with nearly all surface electrodes is that they are subject to movement artefacts; movement of the electrode disturbs the electrochemical equilibrium at the electrode/tissue interface and thus causes a change in electrode potential. The input impedance is an important consideration in bioelectric amplifiers because it can cause attenuation of a signal which is derived from electrodes with high impedances.
