eDAQ Picostat, User Manual

Page: 24 / 122

20 eDAQ Potentiostats
When in Potentiostat mode clicking the Calibrate button will zero the
current signal, using the Dummy cell, including any signal due to any
small offset from the e-corder Output at E In. Thus it should be
considered a ‘relative zero’.
Recalibatrion is required after you:
• select a different range for the Potentiostat applied potential,
page 21 ;
• turn iR Compensation on or off, page 20 .
• change from Potentiostat to ZRA operating mode;
• change from ZRA to Potentiostat operating mode. However, to get
true absolute current measurements in Potentiostat mode
(independent of small offsets at E In) first calibrate in ZRA mode and
then switch to Potentiostat mode without recalibrating.
Note that, in all cases, the Calibrate button does NOT remove
background current signals due to actual electron flow in the real cell.
iR Compensation
iR compensation is available only when in Potentiostat mode. Positive
feedback compensation is used.
When the iR Compensation panel is on, then the degree of iR
Compensation can be adjusted using the slider bar. First adjust the
applied potential to a value where no Faradaic process occurs, use the
buttons for fine control. Now use the slider bar to gradually increase
the amount of compensation until the current signal goes into
oscillation, then decrease the compensation until stability is restored.
For very fine control of iR Compensation use the
Test checkbox. This
applies a small perturbation (1 Hz, 10 mV amplitude square wave) to
the electrode. The iR Compensation is adjusted until an appropriate
amount of ringing is seen on the potential signal.
The maximum amount of iR compensation available depends on the
selected gain range,
page 103 .