Linear Sweep Voltammetry Setup Parameters

Save the current parameter set on your disk. This is very useful when you are running repetitive tests. Parameter sets are stored in a file with a .SET file-name extension. More than one parameter set can be stored in each file, with the set distinguished by aSet Name. This system is a powerful tool for organizing your experimental setups. For example, each worker in a lab can have his own setup file (JOE.SET, KAREN.SET, etc.). Within her file, Karen can save multiple parameter sets under descriptive Set Names (C1010 Noise, Fast Noise, etc.).

Clicking Save opens a dialog box which requests the name of the file where you wish to save the parameter set, and the Set Name within in the file. Once you are satisfied with the names, clicking the OK button saves the set in the specified file.

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 Identifier string defaults 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 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.

Enter several lines of text that describe the experiment. A typical use of Notes is to record the experimental conditions for a data set.

To the right hand side of the notes is a button. This button allows you to open theExperiment Notes dialog box, shown below, which shows more of the notes at one time.

You can edit the notes in either place.

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 the most normal punctuation including spaces. tab characters are not allowed in the Notes string. You can divide your Notes into lines using enter.

The pathname of the file in which the output data are written. It can be a simple filename with no path information, where 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 Path 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 Filename 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 box, Unable to Open File, appears. 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 box where you can enter a new filename.

The ending potential in a linear sweep voltammetry scan. This potential can be selected versus E_oc or versus E_ref. This potential is entered in volts (V).

The speed of the potential sweep during data-acquisition. The Scan Rate is entered in units of mV/s. A practical bound on the Scan Rate is 1000 mV/s. You may try higher scan rates, but they can yield inaccurate data because of the inability of the software to acquire data points fast enough. Scan Rate combined with Step Size determines time between data points, and thus the data-acquisition rate in the experiment.

Time (s/point) = [Step Size (mV/point)] / [Scan Rate (mV/s)]

The maximum data-acquisition rate depends on the speed of the computer, the configuration of Windows^®, and the other software currently executing. As a guideline, avoid sample times < 100 µs. For scans faster than 1 ms, the acquired data is only displayed after the experiment is dine. This reduces the chance that the computer limits the acquisition speed.

The spacing between the data points in mV. A typical Step Size setting is between 1 and 5 mV. The Step Size parameter combines with the scan range on any given cycle to determine the number of data points.

# Points = [Scan Range (mV)] / [Step Size (mV)]

The total number of data points must be less than 64 000 for all cycles. The Step Size parameter also combines with the Scan Rate parameter to determine the time interval between the data points.

Choose theAuto radio button or Fixed radio button.

If set to Auto then the I/E Range changes depending on the measured current to optimize the current resolution/error. Autoranging does not work well for very small currents or for faster sample periods. Do not use Auto with sample periods faster than ~1 s.

We recommend Fixed mode, which sets the I/E Range based on the Max Current specified below.

The Initial Delay phase of the experiment is the first step to occur in the experimental sequence. This phase of the experiment stabilizes the open-circuit voltage of the sample prior to any applied signal, and to measure that open-circuit potential.

The Initial Delay is turned On or Off via the check box in the Setup dialog. The Initial Delay Time parameter is the time that the sample is held at the open-circuit potential prior to the scan. The delay may stop before the Initial Delay Time if the Stability criterion for E_oc is met. The units for the Initial Delay Time are seconds. The minimum time is one second. The maximum time is 400000 s (more than 4 days). Below 1000 seconds, the time resolution is 1 s. Between 1000 and 10000 s, the resolution is 10 s, and above 10000 s it is 100 s.

In many cases, you really do not want to delay for a fixed time. What you really want is to delay until E_oc stops drifting. The Stab. parameter allows you to set a drift-rate that you feel represents a stable E_oc. If the absolute value of the drift-rate falls below the Stability parameter, the Initial Delay phase of the experiment ends immediately, disregarding the programmed Initial Delay Time. Enter a Stability setting of zero to assure that the delay will last for the full Initial Delay Time. The units of Stab. are mV/s. A typical value is 0.05 mV/s. The upper limit in this parameter is 8 V/s, well above the range of practical stabilities with real cells. The lower limit of the Stab. parameter is set by your patience. A stability of 0.01 mV/s means that a 1 mV drift takes 100s. The software will always take data long enough to resolve a 1 mV change in the potential at the requested drift rate.

No open-circuit voltage measurement occurs if the initial delay is turned off. In this case, the open-circuit voltage defaults to 0.0 V.

The Advanced Pstat Setup checkbox, if checked, opens the Hardware Settings window, to control specific aspects about your hardware. If you are not an advanced user, or simply wish to use the default hardware settings as specified in the scripts, just un-check this box. If, however, you wish to specifically set some hardware items, check this box. The Hardware Settingswindow appears similar to the picture depicted below.

The Electrode Setup checkbox, if checked, opens the Electrode Setup window, to control specific aspects about your electrode. If you are not an advanced user, or simply wish to use the default electrode settings, just un-check this box. If however, you need to specifically set the electrode type or stir/purge conditions, some hardware items, check this box and you will be presented with further options upon clicking the OK button. The Electrode Setup window looks similar to the picture depicted below.

The electrode types are:

If you select a Rotating electrode, an additional setup window appears.

In this setup window you specify the Rotation Speed of the electrode. This speed is entered in Revolutions Per Minute (RPM). If you wish to stop the rotation at the end of the experiment, select the checkbox to turn off rotation after the experiment.