Sensitivity Model for Residence Times Difference Fluxgate Magnetometers Near Zero Magnetic Field

Residence times difference (RTD) fluxgate magnetometers measure the magnetic field using the time difference between positive and negative pulses of the induced voltage signal in the time domain. Sensitivity is one of the most important parameters to evaluate the performance of the magnetometers. According to our best knowledge of existing literature, for the RTD fluxgate sensors, there are no available models that can clearly set up relationships between physical parameters of an RTD fluxgate and the sensor sensitivity. Moreover, the relationship between the sensitivity and the excitation conditions is very complicate, thus the sensitivity calibration process is time-consuming. This paper presents a sensitivity model at a near-zero magnetic field. According to the model, by using relevant parameters of the excitation coil and driving signal, and the hysteresis state of the magnetic core, accurate predictions of sensitivity for the sensors can be made. RTD fluxgates with different structures were designed and built to experimentally verify the presented sensitivity model. The testing results indicates that the model is valid and the relative error of its prediction on sensitivity is less than 4%. Using the proposed sensitivity model, we can not only study situations of various excitation signals but also have a theoretical foundation to miniaturize the RTD fluxgate sensors.