Run the Electrochemical Energy Galvanostatic EIS standard technique by selecting Experiment>Electrochemical Energy>Galvanostatic EIS from the Framework™ menu bar. This initiates the following sequence of events:
The cell is turned off and the specimen's Eoc is measured. 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. The potentiostat is switched to galvanostatic mode and the cell is turned on. The measurement parameters are set to measure an impedance equal to the Estimated Z parameter. If a non-zero DC current has been requested, it is generated.
The current equal to the AC current is then output at the Initial Freq. and the cell's response to this frequency is measured. If the readings of both the E and I signals are acceptable, the script proceeds to the frequency sweep.
If the values are not acceptable, the script generates a new estimate for the cell's impedance, resets the measurement parameters for this impedance, and reruns the measurement. If an acceptable reading cannot be reached after a set number of attempts, the script reports an error, asks if you want to quit or continue, and waits for your answer.
In the frequency sweep, the script first calculates the desired frequency. For the Nth step in the loop, the frequency is calculated as follows:
Log Increment = 1.0 / Points/decade
If Initial Freq. > Final Freq., then log(Increment) = –log(Increment)
Frequency = 10[log(Initial Freq.) + N × log(Increment)]
This calculated frequency is then adjusted slightly because of the finite resolution of the oscillator and to avoid harmonics of the power-line (mains) frequency.
The script then sets the measurement parameters to measure an impedance equal to the last recorded impedance, and then takes an FRA reading. If the readings of both the E and I signals are acceptable, the script converts the readings to an impedance, records the impedance point on disk, updates the displayed curve, and then proceeds to the next frequency in the frequency sweep.
If an acceptable reading cannot be reached after a set number of attempts, the script reports an error, asks if you want to continue, and waits for your answer.