Integration of the electronics and batteries inside the hollow core of a search coil

A novel design of a miniature search coil magnetometer is proposed based on the integration of the electronics and batteries within the hollow core of the search coil. In contrast with conventional designs, where the search coil and its electronics have individual housings and electrostatic shields, this paper presents a design in which the core of the search coil serves both as the housing and the magnetic shield for the electronics and batteries. Moreover, the electrostatic shield of the search coil also shields the electronics and batteries. We found that a thin-wall tube core with sufficient permeability is able to replace a solid rod core without decreasing the average flux sensed by the coil winding. In addition, the outer diameter of the tube core can be increased beyond its optimum size to provide more space for the electronics and batteries without considerably affecting the search coil resolution. To validate the effectiveness of this new design, a miniature search coil magnetometer was built and tested for very low frequencies and ultra-low power consumption.