Abstract: A device for measuring the density of liquids. A float provided with a piece of soft iron on one side and with a permanent magnet on the other side is movably disposed in a housing through which a liquid may flow. The soft iron is surrounded by a differential winding, and the permanent magnet is surrounded by two windings with opposing fluxes and having substantially the same numbers of ampere-turns. An output lead from the differential winding is connected to the windings surrounding the permanent magnet over an amplifier. A measuring instrument connected between the amplifier and the windings surrounding the permanent magnet provides an indication of the density of the liquid flowing through said housing.