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Abstract
The design and performances of a high dynamic range DC-AC current sensor utilizing Giant Magneto-Impedance (GMI) are presented. The sensor is based on a GMI element with negative feedback. The sensing element is a 30 μm diameter GMI Co-based amorphous wire. It is curled to a toroidal core of 2 cm diameter. A bias magnetic field of about 650 A/m is applied to the GMI element to obtain an asymmetric GMI effect. A strong negative feedback is introduced to ensure linearity in a wide dynamic range. Analog conditioning electronics was fully developed. This includes a square wave oscillator based on an inverter trigger; a peak detector and a high gain amplifier with zero adjust. The GMI element is driven at a 3 MHz frequency and 5 mA peak-to-peak current. The closed-loop operations are investigated and the performances of the sensor are presented. DC current measurements are performed. The sensor exhibits good sensitivity and very good linearity, free from hysteresis, in a wide dynamic range of ±40 A. The sensitivity is about 0.24 V/A and the linearity error is about 0.02% of the full scale (FS). The hysteresis error is smaller than the measurement accuracy. AC current measurements using the developed sensor have also been successfully achieved. The sensor bandwidth in closed-loop was about 1.7 kHz.
Highlights
Giant Magneto-Impedance (GMI) is a large change of the AC impedance of some soft magnetic materials when they are subjected to an external DC or low-frequency AC magnetic field [1]
Unlike the work presented in [18], we show that the optimization of the sensor allows achieving a very good linearity and a quite reasonable sensibility in a high dynamic range of ±40 A for application in power systems
The well-known temperature dependence, which is the subject of our current work, is expected to be reduced by the use the negative feedback, since, once again, the gain in closed-loop is less dependent on the GMI characteristics than the open-loop gain
Summary
Giant Magneto-Impedance (GMI) is a large change of the AC impedance of some soft magnetic materials (such as amorphous wires or ribbons) when they are subjected to an external DC or low-frequency AC magnetic field [1]. We present the full design and development of a linear current sensor using amorphous wire with both field biasing and strong negative feedback. Unlike the work presented in [18], we show that the optimization of the sensor allows achieving a very good linearity and a quite reasonable sensibility in a high dynamic range of ±40 A for application in power systems. In this context, low frequency AC current measurements have been successfully performed using the developed sensor. Circuits were fully designed and the operation principles of the sensor in both open- and closed- loops are analyzed to help the reader in reproducing the design with a minimum development time
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