To compare the two types of perturbation signals, the PEFC was operated under normal conditions while applying AC perturbations, alternating between the multisine and WF signals from Figures 2b and 3b respectively. A 40 s sample of the cell voltage can be seen in Figure , highlighting the regions where each perturbation was applied. Figure highlights that, for the same perturbation amplitude, the WF signal is able to generate a response in the cell voltage that is approximately two times larger than that generated by the multisine signal; it is, therefore, easier to differentiate between the WF response and the normal voltage noise of the PEFC. In comparison, the low signal-to-noise ratio of the multisine signal can result in measurement errors when passed through subsequent machine learning (ML) algorithms, since it becomes harder to distinguish between the AC voltage response and the normal voltage noise, as discussed by Giner-Sanz et al. . Obtaining a similar response amplitude with the multisine method would require an increase in the perturbation signal amplitude. However, this is detrimental since the system needs to be maintained in a steady state; thus, the perturbation amplitude must be large enough to avoid measurement errors but small enough to prevent deviation from the normal operation. Therefore, the WF perturbation appears to be superior to the multisine signal since, for the same amplitude, it can generate a larger voltage response in the PEFC, solving the issue of excessive perturbation amplitude faced in previous work .