Design of a DC Current Sensor Based on Fluxgate Principle

Precise DC current measurement has been one of the important topics of metrology science as a result of technological developments in diverse sectors of the industry, e. g. nanotechnology. In order to measure DC current, different techniques based on various working principles have been developed. Those are well described in references . On the other hand, these current sensors have an accuracy of between 0.5 and 2%. According to Ripka et al, high-precision measurement of DC current can be ensured by using fluxgate principle . In the present work a current sensor based on fluxgate principle was designed for the measurement of small DC currents. It consists of two coils wound on toroidal ring core from cobalt-based amorphous Metglass 2714A ribbon. The inner primary coil was driven by proper excitation signal and the magnitude of the second-harmonic voltage (2f signal) induced by the outer secondary coil was evaluated to be the sensor signal. The DC current in a wire inserted through the center of the toroid was measured as independent variable. The results presented in the paper show that a good linear relation between the magnitude of the DC current and the 2f signal can be achieved. 2. EXPERIMENTAL PART The sensor shown in consists of two coils, primary and secondary, used for excitation and signal detection, respectively. The core of the sensor consists of 10 turns of amorphous ribbon wound on polyether ether ketone (PEEK) support having a diameter of 10 mm . The material of the core is from Metglas 2714A ribbon with a thickness of 15 µm and width of approximately 3.2 mm.