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Measurement of Small-current Signals – Floating Operation
79
EIS Speed
In EIS, do not expect the Reference 3000 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 3000.
Z
·
f
< 10
9
·Hz
Ancillary Apparatus
Do not use the Reference 3000 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 3000 cell leads.
Floating Operation
The Reference 3000 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 3000’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 3000 is operated in a floating
mode. The instrument specifications only apply on isolated cells with the Reference 3000 earth-ground
referenced (not floating).
Special precautions must be taken with the cell connections when the Reference 3000 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 3000 from earth ground.
Finally, ancillary apparatus connected to the Reference 3000 must be isolated. External voltmeters, ammeters,
FRAs, etc. must be isolated. This includes devices connected to the monitor connectors located on the
Reference 3000 rear panel.