Gamry Instruments Reference 30k Booster Operator's Manual page 19

Figure 2-1 shows a simplified schematic of the Reference 30k Booster connected to a Reference 3000
Potentiostat. The diagram shows the connections for potentiostatic operation using half-cell connections to a
three-electrode cell.
The electrochemical cell under test is depicted on the right side of the diagram. The cell has connections to
both the Reference 30k Booster and the Reference 3000 potentiostat as follows:
• The Reference 3000's Reference lead and Working Sense lead connect directly to the cell. These leads
sense the voltage-difference between two points in the cell. In three-electrode cells, this is usually the
voltage between the working electrode and a reference electrode. In two-electrode cells, this is the
voltage across the two available cell terminals
• The Counter and Working Electrode connections can carry very high currents. The high-current
terminals on the Reference 30k Booster are usually connected to the cell using a heavy, large diameter
cable.
Whenever possible, use the Reference 30K Booster with the high-current cell cable shipped
with the unit. This cable has been specially designed for low inductance. Use with other cables could result
in control-loop oscillation.
In Figure 2-1, note that the Working and Counter connections are switched within the Reference 30k Booster.
When the system is on the 30 A current range, a switch connects the Counter electrode to the output of the
Reference 30k Booster's 30 A power amplifier. The input voltage for this high-current amplifier comes from the
voltage on the Reference 3000's Counter electrode lead. A second switch connects the working electrode to
the 30 A current-measurement circuit. The output of this current-measurement circuit is converted into a 3
mA current and connected to the Reference 3000's Working Lead.
On all other current ranges, the system operates in its pass-through mode. The switches described above
connect the high-current Working and Counter Electrode terminals to the lower current Reference 3000 cell
leads.
While the system does treat the Reference 30k Booster as an additional current range,
Gamry's software does not allow auto-ranging between the 30 A range and the lower ranges. The transition
between the boosted and non-boosted ranges can only be made when the cell is turned off.
The high-current cable connecting the cell to the Reference 30k Booster is not shielded. This cable is optimized
for low inductance, not low capacitance. The lack of shielding generally allows significant noise pick-up in the
system, especially at the power-line (mains) frequency of 50 or 60 Hz. This noise is usually large enough to
preclude use of sensitive current ranges in pass-through mode. Gamry's software currently does not allow pass-
through mode to use ranges more sensitive than 30 mA full-scale.
Introduction – Theory of Operation
19