Potentiostat Stability

Potentiostats by their nature are prone to oscillation especially in experiments like cyclic voltammetry where researchers want to minimize the uncompensated resistance in their electrochemical cell. These oscillation problems tend to be most troublesome when the more sensitive current ranges are used and when the cell capacitance is large. Modern potentiostats have several different methods of minimizing oscillation of which two are the ability to control the control amplifier speed and also to essentially add a filter in the current-to-voltage conversion circuit. (The control amplifier is the circuitry that maintains the desired voltage or current in an electrochemical cell) In both these cases, the different settings involve placing a capacitor across the relevant circuitry.

Another trick which is often successful with high capacitance cells is to add resistance to the COUNTER electrode lead. This makes the potentiostat work harder by requiring a greater potential at the potentiostat's counter electrode lead. This has the effect of slowing down the potentiostat, making it less prone to oscillate.

Sometimes the reference electrode can cause problems if it responds slowly. This can be alleviated by placing a capacitively coupled wire (for instance a platinum wire) in parallel with the reference electrode. This allows for a high frequency response to changes in the voltage while maintaining the actual DC potential. Using a capacitively coupled reference electrode in an electrochemical impedance spectroscopy experiment can improve the high frequency results.