Accurate measurement of magnetic fields holds immense significance across various disciplines, such as IC circuit measurement, geological exploration, and aerospace. The sensitivity and noise parameters of magnetic field sensors play a vital role in detecting minute fluctuations in magnetic fields. However, the current detection capability of tunneling magnetoresistance (TMR) is insufficient to meet the requirements for weak magnetic field measurement. This study investigates the impact of structural and fabrication parameters on the performance of TMR sensors. We fabricated series-connected TMR sensors with varying long-axis lengths of the elliptical cross-section and adjusted their performance by modifying annealing magnetic fields and magnetic field bias along the easy axis. The results demonstrate that TMR sensitivity decreases with increasing long-axis length, increases initially and then decreases with an annealing magnetic field, and decreases with a higher bias magnetic field along the easy axis. The voltage noise level of TMR sensors decreases as the long-axis length increases. Notably, the detection capability of TMR sensors exhibits a non-monotonic dependence on long-axis length. Moreover, we optimized the hysteresis of TMR sensors by applying a magnetic field bias along the easy axis. When the bias along the easy axis reached 16 Oe or −40 Oe, the hysteresis level was reduced to below 0.5 Oe. After encapsulating the TMR devices into a full Wheatstone bridge structure, we achieved a detection capability of 17 nT/$\sqrt{\mathrm{Hz}}$@1Hz. This study highlights that the detection capability of TMR devices is jointly influenced by fabrication parameters. By optimizing parameter configuration, this work provides theoretical guidance for further enhancing the performance of TMR devices in magnetic field measurements.

The demand for innovative digital grid technologies necessitates the development of high-frequency current measurement techniques, extending into the tens of MHz range, to enhance power grid monitoring capabilities and monitor discharges in power equipment. However, monitoring of high-frequency partial discharge current remains challenging for the current sensor because of limitations imposed by the restricted bandwidth of the magnetoresistance chip and the back-end circuitry of the sensor. Therefore, a 20-MHz wideband current sensor is designed employing a tunnel magnetoresistance (TMR) bridge chip optimized for the frequency band. The factors that affect the bandwidth limitation of TMR current sensors are examined. On one hand, by enhancing the frequency response of the TMR chip, we successfully fabricated chips with a bandwidth exceeding 50MHz, representing a significant improvement compared to commercially available chips limited to only a few megahertz. On the other hand, optimization strategies were implemented for expanding the bandwidth of printed circuit board integrated TMR current sensors, resulting in a maximum achievable bandwidth of up to 20 MHz. The developed sensors were tested to measure the discharge current in a needle-plane electrode, thereby confirming their suitability for high-frequency discharge current measurement.

The integration of numerous distributed energy resources and power electronic devices introduces a wide spectrum of frequency disturbances, which significantly challenge the stability of modern power systems. Therefore, there is an urgent need to enhance the current monitoring level of modern power systems. This paper proposes a novel busbar current inversion scheme based on an elliptical magnetic sensor array. By establishing a simulation model, the effect of structural parameters of the elliptical array on its current measurement accuracy was analysed. The anti‐interference capability of the elliptical array in complex environments such as busbar displacement and crosstalk was studied, and principles for designing array parameters under different current sensor standards were established. Experiments conducted on the proposed current sensing scheme demonstrated that the designed current array has a range of 0–150 A, with a current measurement error below 0.1% without external interference and not exceeding 1% during busbar displacement. Under conditions of crosstalk, the measurement accuracy achieved was class 0.5. The sensor array possesses high measurement accuracy, robust anti‐interference capability, low power consumption, compact size and a noncontact nature. It exhibits significant potential for extensive application in novel business scenarios within the power system.