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Try to avoid:
• Narrow-bore or glass-frit-tipped Luggin capillaries.
• Poorly conductive solutions, especially in Luggin capillaries.
• Asbestos-thread and double-junction reference electrodes.
Reference electrodes often develop high impedances as they are used. Anything that can clog the isolation
frit can raise the electrode impedance. Avoid using saturated KCl-based references in perchlorate-ion
solutions.
Instrument Settings
There are several things to remember in setting up a very sensitive experiment.
• In EIS, use the largest practical excitation. Don’t use a 10 mV excitation on a coated specimen
that can handle 100 mV without damage.
• Avoid potentials where large DC currents flow. You cannot measure 1 pA of AC current on
top of 1 mA of DC current.
EIS Speed
In EIS, do not expect the Reference 600+ to measure 10
13
Ω impedances at 1 kHz. Many of the factors
listed above limit the performance.
As a rule of thumb, the product of impedance, Z, times frequency, f, should be less than 10
9
·Hz for good
EIS measurements with a Reference 600+.
Z · f < 10
9
·Hz
Ancillary Apparatus
Do not use the Reference 600+ with ancillary apparatus connected directly to any of the cell leads.
Ammeters and voltmeters, regardless of their specifications, almost always create problems when
connected to the Reference 600+ cell leads.
Floating Operation
The Reference 600+ is capable of operation with cells where one of the electrodes or a cell surface is at
earth ground. Examples of earth-grounded cells include: autoclaves, stress apparatus, pipelines, storage
tanks and battleships. The Reference 600+’s internal ground is allowed to float with respect to earth
ground when it works with these cells, hence the name “floating operation”.
Instrument performance can be substantially degraded when the Reference 600+ is operated in a floating
mode. The instrument specifications only apply on isolated cells with the Reference 600+ earth-ground
referenced (not floating).
Special precautions must be taken with the cell connections when the Reference 600+ must float. Make
sure that all the cell connections are isolated from earth ground. In this case, you must disconnect the
chassis-ground terminal of the Reference 600+ from earth ground.
Finally, ancillary apparatus connected to the Reference 600+ must be isolated. External voltmeters,
ammeters, FRAs, etc. must be isolated. This includes devices connected to the monitor connectors located
on the Reference 600+ rear panel.
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