The EIS technique can be implemented in twoways, namely, the
in-situ and ex-situ technique. The in-situ test is often used for a
single fuel cell or a fuel cell stack. Integrated systems that are
adapted to the in-situ measurement have not been thoroughly
investigated because of the complexity of the in-situ test system.
Therefore, the ex-situ test is preferred by many fuel cell
researchers.