This paper describes the results of an applied novel design methodology for engineering optimised macroscale fluxgate sensors for low-power consumption. The study is used in conjunction with the development of a new fully digital system measuring the Earth’s magnetic field and extracting the necessary parameters for measuring the complex solar wind–magnetospheric–ionospheric system. The results are of interest to the aerospace and defence industries, since macroscale fluxgate sensors exist in airborne and spaceborne systems for many decades. Lowering power consumption is followed by simplification of the accompanying electronic circuits.