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Chapter 5 Operation modes & Parameters 53
C H A P T E R 5
Operation modes & Parameters
Three- or two electrode configuration
The circuitry of the ROXY Exceed potentiostat is designed for operation
with electrochemical flow cells with both a two or three-electrode configu-
ration (Fig. 10). In a three-electrode configuration the working potential is
set between the working electrode (WE) and the auxiliary electrode (AUX).
The AUX is kept at a precisely defined reference electrode (REF) potential
by means of the so-called voltage clamp. This is an electronic feedback
circuit that compensates for polarization effects at the electrodes.
At the WE, which is kept at virtual ground, the electrochemical reaction
takes place, i.e. electrons are transferred at the WE. This results in an
electrical current to the I/E converter, which is a special type of operational
amplifier. The output voltage of the I/E converter is digitized in the instru-
ment by means of a 24-bit A/D converter and processed, and the resulting
output current Ic can be acquired digitally by PC control software (Dialogue
Elite or Chromeleon CDS
) or analog using the ‘Analog Data output’ on the
rear panel connected to a recorder or an external A/D converter.
Fig. 10. Schematic representation of an electrochemical cell and potenti-
ostat electronics operating with a three-electrode configuration.