【作者】 马波；

【导师】 程德福；

【作者基本信息】 吉林大学 ， 检测技术与自动化装置， 2010， 硕士

【摘要】 磁通门传感器是弱磁场测量应用中较为重要的器件,其原理服从法拉第电磁感应定律,其模型类似于变压器模型。根据电磁场理论,利用磁芯的磁滞特性,磁通门将磁信号最终转换成便于测量的电信号。目前,大多数磁通门都是通过检测其输出信号的偶次谐波幅度来测量磁场的,其灵敏度受传感器噪声的制约,需采用差分等能够抑制奇次谐波噪声或带有补偿线圈的探头结构。同时由于传统磁通门需要检测偶次谐波幅度,因而其检测电路较为复杂,后续数据处理也较为烦琐。要提高磁通门的灵敏度、分辨力及精度等性能指标,除了改进制作工艺,提高制作技术水平外,还必须从磁通门的原理入手研究新的检测机理。本文提出了迟滞时间差检测机理,系统地建立了迟滞时间差型磁通门的数学模型,并依此机理完成新型磁通门实体的制作,最终实现高灵敏度、高分辨力的磁测装置的设计。根据电磁场理论建立迟滞时间差型磁通门传感器模型,并推导迟滞时间差同励磁场及待测磁场的关系以及灵敏度同励磁幅度和频率的关系。以迟滞时间差为检测对象,采用高导磁率、高矩形比的钴基非晶合金为磁敏感材料,运用PCB工艺,制作完成一种单磁芯探头结构的新型磁通门传感器。以迟滞时间差型磁通门实体为磁探头,文中完成便携式弱磁测量装置的设计,并实现-4×104nT～+4×104nT弱磁场的标定,其分辨力达到60nT。同传统磁通门相比,传感器的探头结构得到很大的简化,体积有效地减小,易于微型化;检测电路简单,磁测装置的体积也大为减小,易于便携式测量;数据处理简单,测量周期短;在传感器的体积和功耗同时降低的情况下,可以使灵敏度和分辨力等性能指标达到理想。更多还原

【Abstract】 With modern technological advancing, magnetic sensors are developing towards high sensitivity, high resolution, miniature and intelligence. As one of the most important devices in the detection of weak magnetic field, fluxgate magnetic sensor plays a major role. It can measure the weak magnetic field that the range is about 10"10T~10"4T and the resolution is about 10"11 T~10"9T, and also can detect the gradient field and vector field. It is widely used in mineral prospecting, archeology, magnetic field measurement, spacecraft attitude control and other industrial, military and medical fields, and has good development prospects.Traditional fluxgate sensor is based on the general principle of even harmonic which detects the output signal of the even harmonic amplitudes to calculate the measured magnetic field. Its sensitivity subjects to the constraints of fluxgate sensor noise, and requires the use of difference that can inhibit the probe noise or with a compensation coil for reducing the impact of noise. By the level of modern production technology and material constraints, the traditional fluxgates go into the bottleneck of the development.This article will study the design of a new type of fluxgate sensors (namely hysteresis time difference type fluxgate sensor) based on the hysteresis characteristics of magnetic materials and magnetic measurement device. We calculate the time difference between the positive and negative pulse of the induction voltage from fluxgate output, and we can attain the size and direction of the magnetic field. When the excitation current Ie drive magnetic core as the period Te, the core is periodically saturated, and the voltage induced of fluxgate output signal modulate by the magnetic permeability. When the fluxgate is exposed in the zero magnetic fields, the time of negative saturation state is the same with the time of positive saturation state. And therefore the induced voltage signal is a symmetric signal. The time interval between positive pulse and negative pulse is equal to the time between negative pulse and the next period pulse, and the time difference is zero. When the sensor is in the external weak magnetic environment, the time of positive saturation and negative saturation is not the same. Therefore, the induced voltage signal is an asymmetrical signal. The time interval between positive pulse and negative pulse is unequal to the time between negative pulse and the next period pulse, and so the time difference is non-zero. The detection circuit of magnetic measurement device is simpler than that of the traditional fluxgates. Which effectively reduces the size and power consumption, and data processing is also relatively simple. Fluxgate based on hystereis time difference can access to higher resolution and accuracy in the cases of significantly lower power consumption and volume.This paper introduces the background of the study subjects, the development and trend of domestic and foreign fluxgate instrument, and the purpose and significance of the hysteresis time difference magnetic fluxgate and magnetic measurement device are also proposed. In this paper, we also discuss the even harmonics theory, the structure and the measurement circuit of traditional fluxgate. The paper systematically discusses the theory of hysteresis time difference. According to Faraday’s law of electromagnetic induction, we establish the mathematical model of the new fluxgate sensor, and derive the sensitivity expressions of the fluxgate to obtain the ways of optimization. With the combination of the simulation and experiment, we analyze the impacts of the driving signal waveform, amplitude and frequency on the sensor sensitivity. Sensor model simulations by using MATLAB tools are presented. We discuss in detail the structure of the sensor probe, core material and production processes on the sensor performance, and give the fluxgate sensor production program in combination with experiments. To hysteresis time difference for the detection of objects, adopting high permeability, high squareness Co-based amorphous alloy for the magnetic-sensitive material, and using PCB technology, we finally complete one single-core probe fluxgate based on hysteresis time difference. Using direct digital frequency synthesis technology, we design a high accuracy excitation signal generator whose waveform can be switched and the magnitude and frequency can be precisely adjusted. We complete the minimum system FPGA circuit, adaptive amplification as well as hysteresis shaping detection circuit. Power circuit, control and display circuit design and the design of magnetic devices system software are accomplished. According to calibration requirements, we design a high accuracy DC magnetic field device to achieve -4x10~4nT~ +4x10~4nT weak magnetic field measurement and calibration in certain circumstances, and test equipment noise, static characteristics, resolution and sensitivity performance.Finally, the paper summarizes the work. In order to improve the system design, we also present its follow-up design and research suggestions.更多还原