6eDAQ Potentiostats
is internally disconnected, so that an open circuit potential can be
monitored. On an EA161 Potentiostat the auxiliary lead (red) must be
disconnected for an open circuit potential measurement — if connected
to a third electrode (or test point) then a ZRA current signal will be
provided at E Out, Figure 2–3.
The Online Indicator
Located at the bottom right of the front panel is the Online indicator.,
Figure 2–1. When lit, it indicates that the software (such as EChem,
Chart or Scope) has located and initialised the Potentiostat. If the light
does not go on when the software is run, check that the Potentiostat is
properly connected. If there is still a problem, please refer to
Appendix B, page 85.
The Overload Indicator
Located on the left-hand side of the front panel is the Overload
indicator, Figure 2–1. When lit, this indicates that the Potentiostat is (or
has gone) out of compliance, which usually occurs because of an open
circuit or excessive resistance in the electrochemical cell. Higher
resistances can be often be encountered when electrodes are fouled by
the products of electrolysis reactions. The Potentiostat tries to
compensate by increasing the compliance potential (that is, the
potential between the auxiliary and working electrodes). If the
compliance voltage exceeds specification (about 11 V) potential control
of the cell is lost and drifting, or oscillation, of the signal can be seen.
Any data collected during this period is unreliable and should be
discarded.
The Overload indicator will light as soon as there is an overload and
will stay on until the recording has stopped.
If the indicator light comes on repeatedly, and your connections are
good, then try bringing your electrodes closer together, and/or
increasing electrolyte concentration, and/or modifying your
experimental conditions to avoid fouling of the electrodes. Redesigning
your electrochemical cell may be necessary. Normally cells are
designed to keep the reference and working electrodes very close
together, however, when a potential overload occurs, you also need to
consider the distance between the auxiliary and working electrodes.
