The application of a fluxgate excitation circuit with a saturable inductor to magnetic field sensing is described. It is shown theoretically that if the saturable inductor is uniformly wound on a ring core, it does not introduce any second harmonic component when exposed to a uniform magnetic field. Measurement results on a uniformly and non-uniformly wound ring core operated as a fluxgate sensor are presented to verify the analysis. Results are also presented for a ring core saturable inductor design when operated in the fluxgate excitation circuit proposed. Measurements for different winding configurations verify that while the sensor is sensitive to the orientation of the inductor when it is non-uniformly wound, the sensitivity to orientation for a uniform winding is negligible. The circuit may therefore, be accurately applied in magnetic field sensing. (C) 2005 Elsevier B.V. All rights reserved.