Hybrid Microfluxgate and Current Transformer Sensor

• Published in: IEEE transactions on magnetics 2022-08, Vol.58 (8), p.1-5
• Main Authors: Lu, Chih-Cheng, Lin, You-Cheng, Tian, Yao-Zhi, Jeng, Jen-Tzong
• Format: Article
• Language: English
• Subjects: Aluminum; Bandwidths; Chip formation; CMOS; Coils; Current measurement; Current transformer (CT); Current transformers; Dynamic range; Excitation; Hybrid systems; Low temperature; Magnetic cores; Magnetic field measurement; Magnetism; Microelectromechanical systems; microfluxgate; non-contact current measurement; Photolithography; Sensitivity; Sensors; Transformer cores; Transformers; Wires
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2022.3157052

In this work, we develop the hybrid current sensor comprising a microfluxgate and a current transformer (CT) for wide-bandwidth current measurement. The microfluxgate consists of two microcoil chips 3.5 mm \times1.75 mm in dimension made by using the standard Complementary Metal-Oxide Semiconductor MicroElectroMechanical Systems (CMOS-MEMS) 0.35 ~\mu \text{m} process. The aluminum wire-bonding technique is used to construct the top excitation coil surrounding the amorphous soft magnetic core patterned by photolithography and wet etching techniques. Under the optimal excitation condition, the response of the microfluxgate current sensor becomes linear with a maximized sensitivity. The in-house made CT is combined with the microfluxgate driving system to form the hybrid current sensor by using a summing amplifier. The hybrid current sensor has a spectral current noise of 0.4 mA/ \surd Hz at 1 Hz. The maximum sensing range is ±10 A, and the non-linearity is less than 2% within the ±4.6 A range, corresponding to a linear dynamic range of 60 dB in a 10 Hz bandwidth. The hybrid microfluxgate-and-CT sensor has a flat bandwidth from dc to 100 kHz. It has the potential to become a practical miniature device featuring a high-dynamic range, wide bandwidth, and low-temperature drift.