eDAQ Picostat, User Manual

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82 eDAQ Potentiostats
During an experiment control the applied current is by adjustment of the
Output Voltage controls (Chart Setup menu) — this controls the
e-corder
output voltage which in turn controls the current applied by the
Galvanostat. For example, if you have selected an
e-corder Output
Voltage range of 500 mV, and a current range of 50 µA, Table 5–1 ,
you might now wish to do an experiment where the current is held at a
constant 35 µA (or 35/50
×
100 = 70% of the range setting). You
should now set the slider control of the Output Voltage control to a
value of 70% of 500 mV, that is to 350 mV. A positive or negative
Output Voltage determines the direction of current flow (into or out of
the working electrode).
The Chart software Stimulator command (Setup menu) can also be used
to set up pulses, stepped pulses, and staircase ramp waveforms which
the galvanostat will follow. You can also use the Timed Events feature
(Setup menu) to adjust the current at predetermined time intervals after
the start of recording.
Consult the Chart Software Manual for more details of the Output
Voltage, Stimulator, and Timed Events features.
Scope software
Operation of the Potentiostat as a Galvanostat with Scope software is
similar to using Chart software (Macintosh version), see
page 80 .
However, a wider variety of applied waveforms can be generated with
the Scope Stimulator command.
Controlled Potential Electrolysis
This technique is essentially the same as Chronoamperometry with
Chart, page 65 , and is also known as amperometry. A constant
potential is applied at the working electrode which is sufficient to
oxidize or reduce the substrate. As the electrolysis continues the
substrate is eventually completely consumed and the current will
decrease to a residual value. Both the potential and the current flow
can be monitored with Chart software in the same way as for
chronoamperometry. The integrated current (that is, the total charge
transferred) can also be determined by integrating the current signal
(see
Chronocoulometry, page 75 ) and this can be used to determine
the extent of reaction.