Advertisement
Chapter 3 -- Cell Cable Connections -- Normal Cell Connections
Connect both the blue and green cell leads to the working electrode. The working electrode is the specimen
being tested. The blue banana jack connection senses the voltage of the working electrode. The green working
electrode connection carries the cell current. The working electrode may be as much as 1.5 volts above the
circuit ground.
Connect the white pin jack to the cell's reference electrode, such as an SCE or Ag/AgCl reference electrode.
The measured cell potential is the potential difference between the blue and white cell connectors.
Connect the red banana plug to the counter or auxiliary electrode. The counter electrode is usually a large
inert metal or graphite electrode. The counter electrode terminal is the output of the PCI4's power amplifier.
The orange lead is only used in ZRA mode where it senses the counter electrode potential (see following
section). Automatic switching to ZRA mode is possible if this lead is connected to the counter electrode. If you
will not be using ZRA mode, this lead can be left open as long as you insure that it will not short against any
other electrode.
The longer black banana plug is connected on the PCI4 end to Floating Ground. This is the circuitry ground for
the analog circuits in the PCI4. In most cases, this terminal should be left disconnected at the cell end. When
you do so, take care that it does not touch any of the other cell connections.
The shorter black lead is connected to the computer's chassis (earth) ground.
If your cell is a typical glass laboratory cell, all of the electrodes are isolated from earth ground. In this case, you
may be able to lower noise in your data by connecting the longer black cell lead to a source of earth ground.
The short black lead or a water pipe can be suitable sources of earth ground.
Caution: If any electrode is at earth ground, you must not connect the long black
cell lead to earth ground. Autoclaves, stress apparatus, and field measurements
may involve earth grounded electrodes.
If you are measuring very small currents, you will probably find that a metal enclosure completely surrounding
your cell (a Faraday shield) significantly lowers measured current noise. This Faraday shield should be
connected to the short black cell connector. If your electrodes are all isolated from ground, you should also
connect the shield to the longer black lead.
The alligator clip on a cell connection can be removed to access the underlying banana plug or pin jack. If you
need to permanently change the terminations on your cell cable, feel free to remove the banana plugs and
replace them with your new termination. Gamry Instruments can provide additional standard or special cell
cables.
In either potentiostatic or galvanostatic mode, if you do not have a reference electrode in your cell, the
reference lead can be connected to the counter electrode for a two electrode experiment. The potential reading
will be the difference between the counter electrode and the working electrode.
3-2
Advertisement
