Common Potentiostat Setup Parameters

Test Identifier

The Test Identifier is a string that is used as a name. It is written to the data file, so it can be used to identify the data in database or data manipulation programs.

The Test Identifier string defaults to a name derived from the technique's name. While this makes an acceptable curve label, it does not generate a unique descriptive label for a data set.

The Test Identifier string is limited to 80 characters. It can include almost any normally printable character. Numbers, upper and lower case letters, and most normal punctuation characters including spaces are valid.

Output File

The Output File is the pathname of the file in which the output data are written. It can be a simple filename with no path information. In this case the output file is located in the default data directory. The default data directory is specified in the Gamry.INI file under the [Framework] section with a Key named DataDir. This default pathname can be changed using the Paths command under the Options menu.

It can also include path information, such as C:\DATA\YOURDATA.DTA. In this example, the data are written to the YOURDATA.DTA file in the DATA directory on drive C:.

The default value of the Output File parameter is an abbreviation of the technique name with a .DTA filename extension. We recommend that you use a .DTA filename extension for your data filenames. The data analysis package assumes that all data files have .DTA extensions.

NOTE: The software does not automatically append the .DTA filename extension. You must add it yourself.

If the script is unable to open the file, an error message window, Unable to Open File, is generated. Common causes for this type of problem include:

• An invalid filename.
• The file is already open under a different Windows® application.
• The disk is full.

After you click the OK button in the error box, the script returns to the Setup window where you can enter a new filename.

Electroactive Area

The surface area of the electrode (in cm²) exposed to the sample solution.

Area of Overlap

The area overlapping between the electrodes on the crystal faces. The Area of Overlap is typically smaller than the electroactive area in order to remove edge effects and maintain high sensitivity.

Notes

The Notes field allows you to enter several lines of text that describe the experiment. A typical use of Notes is to record the experimental conditions for a data set.

Notes defaults to an empty string. The Notes string is limited to 400 characters. It can include all printable characters including numbers, upper- and lower-case letters, and most normal punctuation including spaces. TAB characters are not allowed in the Notes string.

You can divide your Notes into lines using ENTER.

I/E Range Mode

The I/E Range Mode parameter controls the autorange state of the I/E converter.

• With Auto, the I/E Range will be able to freely adjust based on measured currents.
• With Fixed, the I/E Range will be fixed on a range which is able to measure the current entered in the Max Current parameter. For fast experiments, use Fixed. This setting prevents glitches in the current measurement as the I/E Range resistor is switched.

Max Current (mA)

The Max Current parameter controls the current measurement range when the I/E Range Mode is Fixed. When the I/E Range Mode is Auto, the Max Current parameter specifies the maximum expected starting current.

Enter a Max Current value that is the largest current that you expect to see during the experiment. From this information the software sets the current range used in the experiment. In order to use the most sensitive range that does not overload, the software chooses the current range based on a value that is 89% of the full-scale current range.

For example, when using a PC4/750, if a Max Current of 66 mA is input, the current range is 75 mA. On the other hand, if a Max Current of 67 mA is entered, the 750 mA current range is selected.

NOTE: The Max Current parameter is a current, not a current density. The electrode area is not used in calculation of the current range to use.

If your current data look very choppy and steppy, the problem could be a poorly selected current range. If you enter a Max Current value of 10 mA and the maximum current in your sweeps is only 100 mA, you are only using 1/100th of the potentiostat's A/D converter range. The result is significant quantization error. Rerun the test entering a smaller Max Current in Setup.

If your current data show perfectly flat, horizontal regions, the current has most likely overloaded the potentiostat's current measurement circuits. Check that the value that you entered for the Max Current parameter is larger that the actual measured cell current.

Try rerunning the test with a larger value for the Max Current.