A pump for infusing fluid, the pump including a pumping mechanism, a fluid delivery device, a plurality of electric field sensors, and a measurement component. The plurality of electric field sensors is configured to estimate either an electric field that is associated with a patient, or an electric field that is associated with a fluid path of the pump, or both. The measurement component is configured to receive the electric field estimates from each of the electric field sensors and further configured to measure the difference between the electric field estimates.