eDAQ Picostat, User Manual

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Chapter 4 — The QuadStat 57
remain in Real mode when the dialog is closed — this allows you to
start and stop recording data while the electrodes remain active,
which allows periodic recording of the signal from amperometric
biosensors or
in vivo electrodes without disturbing the environment
around the electrodes.
Please note that when using multiple working electrodes in the same
reaction vessel, with a single reference and single auxiliary electrode,
make sure that all the QuadStat channels are set to the same value
(Standby, Dummy or Real). Running an experiment with some channels
set on Dummy, while others are on Real/Standby can cause incorrect
current signals.
Applied Potential
The Applied Potential control offsets the voltage (up to ±2.5 V) applied
to either the dummy cell or external working electrodes. This potential,
E
off
, is remembered by the QuadStat and will be applied when you
start a scan (on Windows computers, the checkbox
must also be ticked for this to happen). Note that each QuadStat
channel may have a different value for
E
off
.
This potential value will be summed with any external input waveform,
E
in
, from the E In connection on the terminal strip connector on the
QuadStat back panel. The total potential, E
total
= E
off
+ E
in
, must be less
than ±10 V.
If you wish to use the QuadStat exclusively with an external voltage
input (for example with EChem software) then make sure the
checkbox is NOT ticked. This will ensure that all E
off
values are zero.
Zero Offset
The current Offset control can be used to ‘zero’ a background current
signal so that small peaks or transient signals can be more accurately
determined in the presence of a large baseline current signal. First tick
the
checkbox. Then, while the baseline current is being
monitored click the button. It may take a few seconds to zero
the signal. Normally this will suffice to accurately zero the signal, and
you can then choose a more sensitive current range setting to observe