Chapter 8: Measurement of Small Signals--Hints for System and Cell Design
8 - 5
Hints for System and Cell Design
Faraday Shield
A Faraday shield surrounding your cell is mandatory for very low-level measurements. Such a shield
reduces both current noise picked up directly on the working electrode and voltage noise picked up by the
reference electrode.
A Faraday shield is a conductive enclosure that surrounds the cell. The shield can be constructed from
sheet metal, fine mesh wire screen, or even conductive paint on plastic. It must be continuous and
completely surround the cell. Don’t forget the areas above and below the cell. All parts of the shield must
be electrically connected. You will need an opening in the shield large enough to allow a cell cable to
enter the shield.
Gamry offers a Faraday shield called the VistaShield™ that features a transparent window so you can see
your electrochemical test during operation. It can be used with any potentiostat.
The Faraday shield must be electrically connected to the Interface 1000’s Floating Ground terminal.
An additional connection of both the shield and the Interface 1000 Floating Ground to an earth ground
may also prove helpful.
Avoid External Noise Sources
Try to keep your system away from sources of electrical noise. Some of the worst are:
Fluorescent lights
Motors
Radio transmitters
Computers and computer monitors
Try to avoid AC-powered or computerized apparatus within your Faraday shield.
Length and Construction of the Cell Cable
The Interface 1000 is shipped with a 60 cm shielded cell cable. We also offer extended length cables and a
special cable for low-impedance cells as choices at extra cost.
Cell cables longer than 1 meter will result in degraded instrument performance. Increased noise and
decreased stability both can occur. However, with most cells, the instrument will work acceptably with an
extended cell cable, so our advice is to go ahead and try it. As a rule, do not use current-interrupt IR-
compensation with cell cables longer than 5 m.
Do not use the Interface 1000 with any cables not supplied by Gamry Instruments. The Interface 1000
cable is not a simple cable like a typical computer cable. The Interface 1000 cable includes a number of
individually shielded wires contained within an overall shield. We pay careful attention to issues such as
shield isolation, isolation resistance, and capacitance.
If you need a special cable, contact us with your requirements.
Lead Placement
Many experiments with the Interface 1000 involve cells with small capacitances, the value of which may
be important.
Only connect the Interface 1000 ground to earth ground if all components of the conductive
cell are well isolated from earth ground. A glass cell is usually well isolated. An autoclave is generally not
well isolated.
To Next Page
Loading...