The TB4042 toroidal conductivity cell provides a means for measuring solution conductivity in chemically aggressive solutions that corrode, foul, or otherwise destroy, electrode-type sensors. The sensor itself comprises two wound toroids encapsulated in a chemically resistant non-conductor made of polyetherether ketone (PEEK). Measurement is made inductively via a magnetic coupling between the solution and the toroids. Because measurement is made inductively and there are no electrodes that can be affected by erroneous resistances from foulants or coatings, these sensors are virtually impervious to all but thick layers of foulants.