A conductivity sensor, preferably a structure with a pair of magnetic cores with a primary coil wire around a shared member of both cores, and a secondary coil wire around a non-shared section of each core. When part of one core is immersed in a fluid and current is applied to the primary coil, measurements taken at the secondary coils reveal the conductivity of the fluid. The same structure can be used to measure the level of the fluid, and to determine impedance.