| Fluxgate magnetometers (FGM) are vector devices which can measure DC or low-frequency AC magnetic fields in the range up to 1mT by utilizing the non-linearity characteristics of the soft magnetic material core when it is saturated. Now FGM technology is used in many fields, from space exploration to geophysics etc. Both the construction and principle of the fluxgate sensors are introduced in detail in this paper. Especially, we visualize the operation principle of the fluxgate sensors by numerical simulation. Meanwhile, we test the second-harmonic fluxgate magnetometer in open-loop and closed-loop situation. A metallic glass ribbon of composition VITROVAC6025 is chosen here as the magnetic ring-core and we use 64 μs square waveform as the excitation signal. A 16bit AD converted used in testing experiment. Experimental results in our own laboratory of the one dimension open-loop fluxgate magnetometer show that its resolution comes to about 5.68 ×10-11T with a linear dynamic of about 1 ×10 -5T. Meanwhile the closed-loop magnetometer has been studied .The detected magnetic field was compensated by numerically controlled PID. In this situation, the resolution of the fluxgate magnetometer comes to about 0.5nT with a linear dynamic of about 3.3 ×10-5T. The one dimension fluxgate magnetometer has been used to measure the ground magnetic field of our laboratory about 400 hours long. We observed semidiurnal the ground magnetic field oscillation, and the result shows ground magnetic changed approximately down to 12nT daily in our laboratory. This fluxgate magnetometer can also be used in the aerobat, satellite and some other important areas.
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