Tafel Setup Parameters

Here is a Tafel Setup dialog box with its default parameters.

Initial E

 Starting point for the potential sweep during data-acquisition. The allowed range is ±10 volts with a resolution of 1/8 mV. Its accuracy depends on the setting.

Final E

 Ending point for the potential sweep during data-acquisition. The allowed range is ±10 volts with a resolution of 1/8 mV. Its accuracy depends on the setting.

Scan Rate

 Speed of the potential sweep during data-acquisition. The Scan Rate is entered in units of mV/s. A practical upper bound on the Scan Rate is 1 mV/s. Higher Scan Rates may run, but yield unreliable data because the potentiostat's compensation and filtering are set for long time constants. Custom scripts may allow Scan Rates of 1 V/s or more. A lower bound on the Scan Rate is given by the minimum Step Size divided by the longest Sample Period. For scans shorter than 2 V, the slowest Scan Rate is 52.1 nV/s or 0.1875 mV/hour. Multiply these limits by four for scans longer than 2 V.

Sample Period

Spacing between data points. It also helps determine the Step Size of the staircase ramp and the Number of Points in the data curve. The Sample Period sets the length of a step. The height of a step depends on both the Scan Rate and the Sample Period.

Calculate the Step Size and the Number of Points in the scan from

Step Size = Scan Rate × Sample Period

Number of Points = Scan Range / Step Size

The units used for the Sample Period are seconds. The shortest Sample Period we recommend is 0.25 second. The longest Sample Period allowed is 715 seconds. The Step Size is rounded to the resolution of the D/A converter making the steps. The resolution of the D/A converter is dependent on the type of potentiostat you are using. Consult your potentiostat manual for more information. A typical Step Size for a Tafel scan is between 0.1 and 1 mV/step. If the step size has to be rounded to fit the resolution of the D/A converter, the sample period is also adjusted so that the scan rate is correct. The Number of Points must be less than 262 143. If you have more points, the experiment aborts just before the scan phase of the sequence.

NOTE: The Scan Range, defined as the absolute value of Final E minus Initial E, must be less than 8 V.