The fluxgate ring-core internal field

A large number of measured demagnetizing factors for fluxgate magnetometer ring cores of a wide range of cross section shapes have been compiled from the literature and plotted against the core cross-sectional area over the squared mean core diameter. The points group close to a straight line through the origin. The local demagnetizing factor is used and the conversion to the average or the global factor is derived. 3 approximate analytical/numerical calculations of the internal field in the ring core magnetic material are made. The results are close to the experimental data, supporting the conclusion that the demagnetizing factor for thin rings is proportional to the ring cross-sectional area divided by the diameter squared. (Original abstract)