Open Circuit Potential is used to measure the open-circuit voltage (Eoc) of an electrochemical cell. It can be run on all Framework™ systems that include a Gamry Instruments potentiostat.
NOTE: You can use this open-circuit potential measurement regardless of the instrument tier assigned to your Gamry Instruments potentiostat.
Run this test by selecting Experiment > Utilities > Open Circuit Potential on the Framework menu bar. This opens a Setup window similar to shown here:
You can choose to save a graph of Eoc versus time. In the dialog box above, the curve will be 200 seconds long (Total Time) with a potential measurement every half second.
In many cases, you just want to measure cell potential until the cell becomes stable (when Eoc stops drifting). The Open Circuit Potential script allows you to automatically terminate the open-circuit measurement when you feel that Eoc has become stable.
Use the Stability parameter to tell the system your definition of a stable potential. If the absolute value of the Eoc drift-rate falls below the Stability parameter, the Corrosion Potential experiment ends immediately, disregarding the Total Time parameter. The drift rate can never fall below zero, so entering a Stability value of zero assures that the experiment will not end prematurely. The units of the Stability are mV/s. A typical value is 0.05 mV/s. The lower limit in the Stability parameter is set by your patience. For example, a stability of 0.01 mV/s means that a 1 mV drift takes 100 seconds. The DC Corrosion has to take data for nearly 100 seconds merely to resolve this small a change in potential.