Intentional electromagnetic interference is an effective mean to jeopardize the security of integrated circuits. In this paper, we propose a new approach to evaluate the efficiency of magnetic probes used to radiate a disturbance: measuring its impact within the target of the attack, more precisely on the propagation delay of a combinational path. The characterization of five probes carried out using three different integrated circuits is reported. In all cases, bespoke, handmade probes outperform commercial ones. Experimental results also show that the electromagnetic coupling between the probes and the integrated circuits is mainly due to global, bonding wires.