In this paper we are interested in FEM mesh refinement procedure in ECT problems with separated T-R (Transmitter and Receiver probes) probes. Local error estimators used for a posteriori h-type mesh refinement are presented. They are based on the complementarity of the E and H formulations. A new estimator is proposed combining the solutions obtained by feeding alternatively the transmitter and the receiver. This estimator proves to be very accurate compared to classical ones.