A device for measuring an amount of superparamagnetic material comprises a pair of measuring coils and a pair of compensating coils, wherein the coils of a pair are identical to each other. The device also includes at least one direct current generator, a low-frequency generator, and a high-frequency generator, the generators being coupled to the first and second pairs to inject into each of the coils a current having a DC component, a high-frequency component and a low-frequency component, such that the magnetic fields generated by the coils of the same pair are identical. The device also comprises a detector of a component of an electric voltage set at a mixing frequency which is a linear combination of the first and the second frequency.