eDAQ Picostat, User Manual

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Chapter 2 — The Potentiostat 21
Note that iR Compensation is set at the particular applied potential you
have chosen. If you then proceed to do an experiment involving a
potential sweep, the amount of compensation required for complete
compensation will vary during the sweep, and it is possible that the
potentiostat will go into oscillation at some point. To avoid this
happening it is usual to always slightly undercompensate, that is, to
find the point of ideal compensation and then to reduce the setting
slightly. The amount of ‘undercompensation’ is usually determined by
trial and error for a particular experiment.
Before using iR Compensation you should always consider other
methods of reducing the uncompensated resistance. For example, could
the reference electrode be more closely positioned to the working
electrode (perhaps by redesigning your reaction chamber), or could the
background electrolyte concentration be increased? Also check to
ensure that the reference electrode is not clogged or dried out. It is
always best to minimize cell resistance within the reaction chamber
rather than trying to overcome the problem later with the potentiostat.
Applied Potential
The Applied Potential controls are enabled when either the Dummy or
Real cell is selected. It allows you to adjust the voltage applied to either
the dummy cell or external electrodes, depending on the mode
selected.
Applied Current
The Applied Current controls appear when in Galvanostat mode
(replacing the Applied Potential controls), see
Figure 5–17, page 78 .
The controls are enabled when either the Dummy or Real cell is
selected. Use them to adjust the current applied,
Figure 5–19,
page 79 .
On Windows computers, the button advises on the correct values to
be entered into Units Conversion of the current signal channel, see
Figure 5–18, page 78 .