Appendix A — Technical Aspects
91
Picostat
The Picostat is designed to function in potentiostatic mode only, that is it
cannot be used as a galvanostat. A block diagram of its construction is
shown in
.
The Picostat is powered by reg17 V, –17 V and +8 V DC lines
from the
e-corder
, see
. The use of DC power
allows its use inside Faraday cages.
An error voltage is generated from the difference between the voltage
on the Reference electrode and the excitation (command) voltage set by
the
e-corder
unit. This difference or error voltage drives a high gain
power amplifier (VCVS – voltage controlled voltage source) the output
of which is applied to the Auxiliary electrode in such a way as to
minimise the error voltage.
The Picostat, and the electrochemical cell to which it is connected,
forms a composite feedback control system in which the value of the
Auxiliary potential is controlled in such a way as to make the Reference
voltage equal to the desired Command voltage. The current flow in the
Working electrode is the quantity being measured.
Overload
Auxiliary
Reference
Working
Online
Operate
Disconnect
Operate
Hi Z
Ref Amp
Gain
Power Amp
Error
Voltage
Subtractor
Overload
Detector
Front Panel
Back Panel
E In
(Command
voltage)
E Out
(Reference
voltage)
I Out
I
2
C Input
I
2
C Control
Interface
Low–pass Filter
I to V
+
–
Virtual Ground (0 V)
I
2
C Output
Shield
Shield
Figure A–2
Block diagram of the
Picostat.
Содержание Picostat
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