The ability of electrochemical sensors to properly measure wall-shear stress is here considered to use them as potential candidates for time-resolved estimation of a large-scale activity occurring at the flow separation region downstream a bump. The inflow Reynolds number considered, based on the channel full height and the incoming bulk velocity, is Reb=1735 . The methodology implemented consists in combining the electrochemical sensors with Piv measurements and to build an estimation model of a low-order representation of the flow field. This estimation model is based on a multi-time reformulation of the complementary technique originally introduced by Bonnet et al. (Exp Fluids 17(5):307–314, 1994 [1]). The present paper shows the potential of electrochemical sensors for properly resolving the low-frequency flapping mode whose control was recently shown by Gautier et al. (J Fluid Mech 770:442–457, 2015 [2]), and its potential as a candidate to significantly reduce separation.