Analysis and design of a self-oscillating quasi-digital fluxgate current sensor for DC current measurement

In this paper, an open-loop self-oscillating fluxgate-based current measurement method is presented. The proposed sensor does not require the low-pass filter necessary in traditional measurement technologies and does not require an analog-to-digital converter when connected to digital systems. More importantly, although the proposed measurement method is based on the open-loop configuration, its measurement accuracy is close to that of the traditional self-oscillating fluxgate measurement technology based on the closed-loop configuration. Accurate mathematical models are established to describe the basic characteristics of the measurement method, and design criteria of the sensor are proposed. The test results show that the proposed measurement method has good linearity; for example, in the full scale of 100 A, its linearity is about 0.4% and can be improved to below 0.2% when the first-order polynomial fitting method is used.