Power line communication (PLC) seems to be one of the best trade-off between cost and benefit for implementing Smart Grids in industrial context. Unfortunately, industrial environment may compromise the reliability of PLC technologies due to noisy communication channel and interfering/competing PLC systems. In this work, a multi-protocol instrument for PLC performance estimation is presented. The proposed solution is able to characterize and to decode several PLC systems with different physical modulations using a software-defined architecture. A working prototype of the proposed instrument has been characterized and used in a real industrial plant in order to study potential issues affecting PLC.