Fluxgate sensors are one of the most versatile magnetic field sensors, offering very reliable field measurement from mT to sub uT region, with very high resolution. Vector magnetic field measurements of better sensitivity are only possible with quantum affects based magnetometer ‘SQIUD’ (super conducting quantum interference device). These sensors require superconductive material for the field detection, which can be maintained only at extremely low temperature (-198o C). Hence SQUID, based systems are very fragile, bulky and costly in operation. The above-mentioned shortcomings of SQUID sensors leave fluxgate as the best choice for the applications, where available space and power is limited (ex. satellite, submarines). The objective of this research is to analyze and optimize these micro-machined magnetic fluxgate sensors for high sensitivity and directionality at low excitation current.
For advanced applications, fluxgate sensor should offer high magnetic field sensitivity as well as directionality. There has been a large demand for the integrated fluxgate sensors containing sensor and the supporting circuit on the same chip. Since CMOS circuits have driving current limitations, main motivation of this research is to optimize sensor core geometry to achieve high sensitivity and directionality at low operating current In this work, first, fluxgate sensors have been simulated by help of finite element analysis. Complete sensor response can be obtained by these simulations and hence different sensor designs can be analyzed before fabrication.
In this work by changing the core shape, excitation current of the sensor has been reduced multiple times, which results in drastic reduction in overall power consumption. Different core geometries are also analyzed for directionality optimization.
After finite element analysis, fluxgate sensors have been simulated and analyzed by the help of an innovative SPICE model. By simulating the sensor in SPICE, an integrated sensor response can be analyzed before fabrication and complete system optimization can be achieved. An innovative SPICE model for ring-core type fluxgate sensor has been developed, which includes saturation and hysteresis phenomenon of magnetic core. The presented model has been successfully applied to fabricated ring-type fluxgate sensors and very good matching has been observed between the simulated and measured values.