A theoretical and experimental study is made of a device that measures the conductivity and velocity of plasma streams. The instrument consists of a primary coil and several secondary coils. Alternating current through the primary coil produces an oscillating magnetic field in the shape of a dipole. Positions of the secondary coils relative to the primary are such that they respond to distortions of the applied magnetic field of the primary that are brought about by the presence and motion of an electrically conducting fluid. These signals on the secondaries vary linearly with the conductivity and with the product of conductivity times velocity. Various possible coil arrangements and the results of tests conducted with a simple three coil configuration in an electric arc jet are presented. Details of the probe tested, its calibration, and its theoretical basis are described. Results obtained with the three coil system are in good agreement with theory.