Design And Implementation Of Single-axis Fluxgate Magnetometer With High Precision

As a magnetic field measurement instrument, Fluxgate magnetometer directly measures the external magnetic field component, which is based on the saturation magnetization of soft magnetic materials. Fluxgate sensor behaves some properties such as simple structure, small size, good shock resistance and higher precision. It has been widely used in scientific research, national defense construction, industrial production and daily life.This project is supported by National Natural Science Foundation to research and develop fluxgate sensor with high-precision, which is used to measure the magnetic field of underwater. Because of the positioning error of inertial navigation system accumulates over time, it must be corrected or re-tune. Conventional method is to receive GPS radio navigation signals, or other active radio navigation signals. Since this method requires underwater vehicles surfaced or near-surface navigation, which greatly reduce theirs hidden and threaten theirs security. It is proposed underwater positioning methods which is based on the magnetic field measurements to solve the problem. Therefore, it is of great significance to research and develop fluxgate sensor with high accuracy, good stability, high resolution and low-power consumption.Through review on both development situation and application of fluxgate sensor at home and abroad, this article studies literature of fluxgate sensor at home and abroad, and discusses the structure and the work principle of magnetometer in details. From the aspect of its mathematical model, we analyse deeply on the magnetic flux gate sensor the output signal of magnetic fluxgate, and select the second harmonic detection scheme. On this basis, we bring forward a implementation scheme of fluxgate magnetometer(Detection circuit modulate fluxgate signal into DC voltage by some circuit module, such as resonance, second harmonic amplification, band-pass filter and second order Butterworth low-pass filter), and complete signal detection and processing circuit design of the open-loop fluxgate sensor. Finally, we complete the whole circuit debugging and preliminary experimental test.Fluxgate sensor composed of analog circuit has the most obvious shortcoming of poor temperature capability, and however the sensor circuit by digital signal processing can greatly improve its temperature capability. Currently, less research of digital signal processing by FPGA on the fluxgate output signal had done at home. In this paper, a implementation scheme of a digital flux sensor is given, and a digital fluxgate sensor circuit based on its analog circuit is designed. The sine wave signal generated from fluxgate circuit is collected by AD974 and digitally processed by FPGA and PID controller, and then returns to the feedback loop by AD7836. We complete the design of a digital fluxgate sensor circuit and program of each module, and carry out functional simulation of every module for the overall system, the results prove primarily the validity of the scheme and software design.