The
electronic circuits employed for measuring electrode voltages and electrode
currents can appear to be very complicated but, in practice, depend on two
basic and simple circuits using field effect transistors (FET) in the form of
operational amplifiers (OPAMPS). There
is a number of different FET OPAMPS that are suitable for the purpose but the
TLO81 OPAMP is readily available, relatively inexpensive and will be used in
this discussion to illustrate the circuitry employed.