Practical Use of the GMI Effect to Make a Current Sensor

This paper deals with practical issues and solutions related to the use of the giant magnetoimpedance (GMI) for electrical current measurement. It presents an overview of a full attempt of design and realization of an almost industrial GMI-based current sensor or clamp. The sensor combines dc and ac measurements with the same flexible sensitive element. This paper addresses several practical problems encountered in a real measurement environment. In this context, main attention was paid to the impact of the influence quantities that largely condition the implementation strategies and solutions of the sensor. For the intended industrial application, these influence quantities first include the operating temperature. Its impact on the intrinsic sensor response was investigated in an almost industrial temperature range. Second, bending stress on the sensitive element is another involved influence parameter in the toroidal and flexible structure of the sensor. The effect of this was also characterized. Finally, the third considered influence parameter is the effect of magnetic disturbances. These include the eccentricity of the conductor of interest and the impact of the surrounding magnetic fields such as the earth's field or fields produced by other conductors in close proximity to the sensor. Different strategies of implementation and solutions, taking into account the impact of influence parameters, were proposed and compared. A sensor prototype was realized, and its first performances were given.