A sensor/transducer for use in reducing leakage current from a patient fluidly connected to a medical device by tubing filled with a conductive fluid (e.g., blood or dialysate (a “fluid line”)) includes a magnetically conductive core with 1) a centrally located support for a coil of fluid line, and 2) coiled electrical conductors located at positions that are spaced from the centrally located support, on opposite sides of the centrally located support. The sensor/transducer can be used to measure leakage current carried by the conductive fluid in the fluid line, or it can be used to induce current in the fluid line in a manner that reduces the leakage current.