Fluxgate-based weak direct current detection system and method

Abstract

The invention relates to a fluxgate-based weak direct current detection system and method. The system comprises an excitation unit, a fluxgate probe and a signal processing unit which are connected in a closed loop; the excitation unit is used for adjusting and outputting an excitation signal to the fluxgate probe, so that an iron core is in an alternate critical saturation state, and a magnetic core always works near a zero field; and the signal processing unit is used for extracting a second harmonic component from the output signal of the fluxgate probe. According to the fluxgate-based weak direct current detection system and method,the duty ratio of the excitation signal is controlled, an output current value is changed, and the current feedback loop is formed, the annular iron core always alternately works in the critical saturation state, and the power consumption of an excitation winding is reduced; the whole system is a closed-loop system, a main controller adjusts output signal parameters to compensate the change of an external magnetic field in real time, so that the magnetic core always works near the zero field, the linearity and the observation range of the system are improved; and the double-closed-loop control ensures that the fluxgate probe works in a relatively optimal state, and the detection stability and sensitivity are improved.

Description

technical field [0001] The invention relates to the technical field of weak signal detection, in particular to a fluxgate-based weak DC current detection system and a method thereof. Background technique [0002] At present, most of the detection methods for DC current are based on the measurement of magnetic field changes, such as the Hall sensor detection method and the magnetic modulation detection method. Among them, the Hall sensor technology is mature, and it is characterized by firm structure, long service life, wide measurement current range, High current measurement accuracy is high, and it is widely used in all walks of life. But it also has its shortcomings. For the open-loop Hall sensor, it is greatly affected by temperature, and the accuracy is low in places where the temperature changes greatly. Long, anti-interference ability is poor, if you want to improve the measurement performance of the sensor, you must use a Hall element with better performance, but its...

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Problems solved by technology

[0004] However, the stability and accuracy of the excitation signal waveform of the traditional fluxgate current sensor is not high enough. The existing technology is to make the fluxgate iron core in an oversaturated state, and the excitation magnetic field strength amplitude Hm is considerably larger than the iron core saturation magnetic field strength Hs The ratio of , so that the relative permeability μ r The value changes periodically from the maximum value to the minimum value, so as to obtain a strong fluxgate signal, and the sensor cannot adjust the excitation signal in real time according to the measurement results to make the coil work in the critical saturation state (when the coil works at the critical saturation point, the magnetic flux The sensitivity of the door probe is the highest)

In addition, there is a transformer effect induced electromotive force in the output of the fluxgate probe. When designing the probe, a double magnetic core structure is used to cancel each other out. However, since the magnetic core cannot be completely symmetrical, there is still a transformer differential effect in the output signal, that is, the magnetic The output signal noise of the pass gate, but also the noise of the circuit itself

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