A novel core structure of inner-ringed multi-pitch rods for lightweight induction coil sensor design

A novel inner-ringed multi-pitch rods core structure for lightweight induction coil sensor design, in which the higher-permeability magnetic rods are located in the inner ring of the induction coil, is proposed. The abbreviation for the novel core structure is “IRMPR core structure”. It is theoretically shown that the induction coil sensor sensitivity of the IRMPR core structure is equal to that of the single-rod solid structure. Compared with the traditional single-rod solid magnetic core structure, the mass of magnetic core of the IRMPR core structure is reduced more than 28%, however, the sensor sensitivity is not sacrificed. Besides, the performance of the IRMPR core structures with permalloy and Zn-Mn alloy magnetic cores were tested under 500Hz and 1–22kHz band conditions, and the performance was improved compared with the single-rod structure of the same materials. The results demonstrate the potential for IRMPR core structure application to various induction coils with different inner-ringed magnetic core materials under broadband conditions. The study also provides a method to vary the sensitivity and resonant frequency of the induction coil sensor by changing the magnetic core arrangement. Furthermore, thinner magnetic rod is more cost-effective and IRMPR core structure will be more compact for the integration of the sensors and their electronics within a single housing.