Potentiostatic OptiEIS Experimental Sequence
Run the Potentiostatic OptiEIS script by selecting Experiment>Electrochemical Impedance>OptiEis Potentiostatic. This initiates the following sequence of events:
- The Framework™ creates a Runner window that will be used to display the experiment while running.
- The script creates the Setup dialog box and accepts changes in the parameters.
- The script now obtains use of the potentiostat that was selected during the Setup, and opens the data file specified during the Setup.
- All input parameters are checked to see if they are valid. If there is a problem, the script returns to the Setup dialog box.
- The file header information is written to the data file. This header information includes: (a) Tags identifying possible analyses; (b) The current time and date; (c) A list of the Setup parameters. This information is written to the file prior to data-acquisition. If the experiment is aborted prior to acquisition of the first data point, the output file contains only this information.
- The script conditions the electrode if Conditioning was specified in the Setup. Conditioning is done by applying a fixed potential for a defined time. It establishes a known surface state on the working electrode. A plot of current versus time is displayed during the Conditioning.
- The cell is turned off and the specimen's Eoc is measured. If an Initial Delay is turned on in the Setup, this step lasts for the time specified as the Delay Time, or until the potential stabilizes. If no Initial Delay is specified, this step only lasts long enough for Eoc to be measured. A plot of potential versus time is always displayed. The last measured potential is recorded as Eoc.
- The script then sets up data-acquisition via the following steps:
- The multisine signal is calculated based on the frequency range and amplitude specified during Setup. The phase is optimized so that large constructive interference is avoided.
- The cell is turned on and the signal is applied for two cycles in order to set up the potentiostat’s ranges and offsets for the best signal-to-noise ratio.
- The signal is applied for another three cycles to check that the amplitudes of individual sine waves are well-adjusted (power-leveling).
- The power-leveled signal is phase-optimized a final time.
- The potentiostat is optimized following another two cycles with the new optimized signal.
- The signal is applied to the cell until a stable, low-noise response is observed, or for a maximum of 20 cycles.
- Pressing the F2-SKIP button during any step quits the OptiEIS experiment with no data saved, because the Fourier transform of partial data cycles leads to incorrect answers.