Cell Connections – ZRA Mode Cell Connections
45
If you are measuring very small currents, you may find that a metal enclosure completely surrounding your cell
(a Faraday shield) significantly lowers measured current-noise. Usually, you connect this Faraday shield to both
earth ground and Floating Ground. The Floating ground on the black cell lead is a convenient source of ground.
If any electrode in your cell is connected to earth ground,
only
connect your Faraday shield to the black cell
lead (Floating Ground).
You can remove the alligator clip on any cell connection to gain access to the underlying banana plug or pin
jack. 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 also provide additional standard or special
cell cables.
ZRA Mode Cell Connections
The Reference 3000 can function as a precision Zero-resistance Ammeter (ZRA), which maintains two metal
samples at the same potential and measures the current flow between the samples. It can also measure the
potential of the samples versus a reference electrode.
The cell cable connections for ZRA mode are shown in Table 6-2. The connections are very similar to those for
the potentiostat and galvanostat modes. A second working electrode is substituted for the counter electrode,
and the Orange Counter Sense lead
must
be connected.
Table 6-2
Cell Cable Connections for ZRA Mode
Color
Type
Name
Normal Connection
Blue
Banana plug
Working Sense
Connect to metal sample #1
Green
Banana plug
Working Electrode
Connect to metal sample #1
White
Pin jack
Reference
Connect to a reference electrode
Red
Banana plug
Counter Electrode
Connect to metal sample #2
Orange
Banana plug
Counter Sense
Connect to metal sample #2
Black
Pin jack
Floating Ground
Leave open or connect to a Faraday shield
The counter sense and the working sense lead are each connected to different metal samples. In the ZRA
mode, the Reference 3000 is normally programmed to maintain zero volts between these leads. It therefore
maintains the two metal samples at the same voltage.
The white pin jack on the cell cable is normally connected to a reference electrode. The potential between
this lead and the working sense lead is reported as the cell potential.
If you don’t have a reference electrode in your cell, we recommend that you connect the white reference lead
to the working electrode. In theory, the measured potential is exactly zero when this is done. In practice, A/D
noise and offset will create a small potential signal with a value very close to zero.
Warning:
Make sure that your earth-ground connection is made to a legitimate source
of earth ground. Consult a qualified electrician if you are uncertain how to obtain an earth ground.
Connecting the Reference 3000 to an incorrect and unsafe voltage can create a safety hazard (see Chapter
1 for details).
