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Fluxgate Technology Principle

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Update time : 2021-09-20 13:16:59
From the late 1960s to the early 1970s, fluxgate technology achieved a significant breakthrough in the accuracy of DC measurements. Its basic principle is to determine the magnitude of the current to be measured by balancing the magnetomotive force generated by the known current through the balance winding in the core and the magnetomotive force generated by the measured current.

The principle of the fluxgate current transducer is shown in the following figure. A is a high magnetic permeability material core. W1 and W2 are proportional windings. I1 and I2 are DC currents supplied by two independent power sources W1 and W2 respectively. Φ1 and Φ2 are magnetic flux generated by proportional windings W1 and W2 respectively. Rm is magnetic resistance.
 
 
Fig. Schematic of fluxgate current transducers
 
According to the principle of magnetic potential compensation in the iron core, when the magnetic potentials are balanced with each other, the current ratio is inversely proportional to the turns ratio. In essence, the fluxgate phenomenon is actually an accompanying phenomenon of the transformer effect, and also obeys Faraday's law of electromagnetic induction. Fluxgate current transducers are based on magnetic modulators and develop in conjunction with modern electronics. The basic principle of the magnetic modulator is to utilize the symmetric nonlinearity of the high magnetic permeability ferromagnetic material. When there is an alternating symmetric excitation field and a DC signal magnetic field in the magnetic modulation core, the iron core is saturated in advance in the half cycle. In the other half cycle, the iron core is lagging behind, and the symmetry of the magnetic flux generated by the excitation magnetic field of the iron core is destroyed, resulting in a difference in the rate of change of the magnetic flux in the positive and negative half-cycles, thereby generating even harmonics.

According to the law of electromagnetic induction, as long as there is a direct current flowing through the transducer, there must be an induced magnetic field, and the induced magnetic field is approximately linear with the direct current passing through the transducer. As long as the induced magnetic field can be accurately measured, the size and direction of the external DC current can be measured indirectly. In addition, through in-depth research, it is found that the fluxgate current transducer modulates the ambient magnetic field generated by the external DC current into an even harmonic induced electromotive force, and not only the even harmonic content is approximately linear with the external DC current within a certain range, but also the average value of the even harmonic content is approximately linear with the external DC current within a certain range.
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