To meet the demand for high-precision, high-resolution measurement of weak currents in smart grids, this article presents the design of a current sensor based on the tunneling magnetoresistance (TMR) effect. To improve the detection accuracy of the sensor, this design adopts a low-noise, high-sensitivity TMR chip as its chip selection; in the sensor circuit, a high-linearity interface circuit is used to eliminate fixed bias; and a magnetic flux concentrator is used to improve sensitivity and anti-interference capability. Experimental results indicate that the sensor achieves a sensitivity of 29.4 mV/V/mA, a linearity of 0.19%, and an accuracy of 0.045% within a ±100 mA range, supporting current measurement from DC up to 10.5 kHz. The proposed sensor demonstrates several advantages, including a wide measurement range, high accuracy, high resolution, and non-invasive measurement capability, making it well suited for weak current detection in smart grid applications.

The detection of current is critical within the context of industrial and power systems. Precise quantification of current is essential to ensure normal equipment functionality, enhance work productivity, and maintain the safety and integrity of power systems. This paper provides an overview of conventional current sensors and highlights the performance differences in current detection. The discussion encompasses current transformers, Rogowski coils, fiber optic current sensors, flux gates, and Hall current sensors. In light of the increasing complexity of current sensing requirements, conventional current sensors face challenges in meeting these demands. Thus, this study presents a comprehensive review of the development and fundamental principles of magnetoresistive sensors. This incorporates anisotropic magnetoresistive sensors, giant magnetoresistive sensors, and tunnel magnetoresistive sensors. Additionally, this paper examines the application of magnetoresistive sensors in current detection. Finally, the paper discusses the challenges and issues faced by magnetoresistive sensors in current detection, alongside the potential for future development trends.