Electrochemical Instrumentation - Roles of Operational Amplifiers and Microcomputers

The conductivity of a solution is measured using an AC bridge with a two-elec-trode conductance cell on one arm (Fig. 5.40(a)) a balance is sought, manually or automatically, by adjusting the variable resistance and capacitance in another arm of the bridge. Usually AC voltage of a few volts and 1 kHz is applied to the cell. The impedance caused by the double-layer capacity at the electrodes does not affect the measured values of conductivity. In some cases, the conductance is measured with a four-electrode cell, as shown in Fig. 5.40(b). For practical methods of measurement, see the reviews in Ref. [25], 

Conductimetry is used to detect and determine ionic species in solution. It plays important roles in environmental analyses and in the detection of ion chromatography. It is also used in acid-base, precipitation and chelometric titrations to detect end-points. However, the biggest advantage of conductimetry is displayed in the fundamental studies of solution chemistry. Its applications to chemical studies in non-aqueous solutions will he discussed in Chapter 7. 

Electrochemical Instrumentation - Roles of Operational Amplifiers and Microcomputers 

The previous sections outlined various electrochemical techniques. For most of these techniques, instruments are commercially available and we can use them conveniently. The common features of modern electrochemical instruments are that operational amplifiers and microcomputers play important roles in them. These are discussed in this section. 

Operational amplifiers, which are the main components of an analog computer, were first used in electrochemical instrumentation at the beginning of the 1960s [26]. Because they are extremely useful in measuring and controlling the electrode potentials and the currents that flow at the electrodes, electrochemical instruments were completely modernized by their introduction. Today, most electrochemical instruments are constructed using operational amplifiers. Knowledge of operational amplifiers will help the reader to understand electrochemical instruments and to construct a simple apparatus for personal use. 

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