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<< Click to Display Table of Contents >> Navigation: Experiments > F - Pulse Voltammetry > Techniques > Square Wave Voltammetry > Square Wave Voltammetry - Experimental Sequence |
Run the Square Wave Voltammetry standard technique by selecting Experiment > Pulse Voltammetry > Square Wave Voltammetry from the Framework™ menu bar. This initiates the following sequence of events:
1.Framework™ creates a Runner window, and the Square Wave Voltammetry.exp script is run in this window.
2.The script creates the Setup dialog box which becomes the active window and accepts changes in the experimental parameters. This Setup window remembers the experimental settings from the last time this script was run. To restore the parameters to the values defined in the script, click the Default button. If the Advanced Pstat Setup is in the On position, a second Setup dialog box containing hardware configuration details becomes the active window, allowing you to modify the hardware configuration used during the experiment.
3.The script now obtains the use of the potentiostat specified during Setup and opens the data file using the Output name. If the potentiostat is in use or the file cannot be opened, the script returns you to the Setup dialog box. The file header information is written to the data file. This information is written to the file prior to data acquisition. If the experiment is aborted, the file contains only this information. This header information includes:
•Tags identifying possible analyses.
•The current time and date.
•A list of the Setup parameters.
4.If you selected a purge time greater than zero, the potentiostat's control bits for purge-gas flow and stirring are turned on. The script delays for the purge time, then turns OFF the stirring and purge-gas control bits.
5.If the electrode is an HDME, a new drop is formed by momentarily activating the potentiostat's New Drop control bit.
6.The script delays for a time set by the Quiet Time parameter.
7.The potentiostat is initialized. The current range is set to a range that allows the measurement of currents as big as the value of the Max Current Setup parameter.
8.The potential is set to Initial E and the cell is turned on.
9.If the Equilibration Time parameter is greater than zero, the script delays for set value.
10.The actual scan occurs.
11.The potential of the sample is set to the staircase potential (Initial E plus N times the Step Height) plus the Pulse Size. This potential is applied for half the period of the square wave. At the end of this time, a current measurement is made. The sign of the Pulse Size is controlled, so that the pulse is always in the direction of the final potential. N is the number of steps that have already occurred. At the start of the scan N is zero.
12.A voltage equal to two times the pulse height is subtracted from the cell voltage. This voltage is equivalent to Initial E plus N times the Step Height minus the Pulse Size. This new voltage is held for half the square-wave period. At the end of this time, a current measurement is made.
13.The difference between the second and first current measurement is calculated and plotted versus the potential prior to the pulse.
14.If Auto-ranging was selected in Setup and the SWV frequency is less than 50 Hz, after each point, the current range is automatically switched to the optimal range for the measured cell currents.
15.Steps 11 to 14 are repeated until the potential prior to the pulse equals the final potential.
16.The cell is turned off. The acquired data are written to the output file. The script pauses to allow you to view the curve you have just collected. Close the curve by clicking the F2-Skip button before attempting to open the data file in the Echem Analyst 2™.