磁阻型弱磁传感器特性自动测试系统

Automated Testing System for Characteristics of Magnetoresistive Weak Magnetic Field Sensors

随着磁阻型弱磁传感器的深入研究和广泛应用,方便、快速的测量传感器低频噪声、灵敏度、非线性等特性已成为研究其低频弱磁场测量能力的基础。设计开发了一套弱磁传感器特性自动测试系统,其自身的噪声平方根谱密度小于槡5 nV/Hz(在10kHz)。它包括亥姆霍兹线圈、惠斯登电桥和低噪声放大器、磁屏蔽桶、高精度数据采集卡和PC等硬件模块,采用互相关功率谱分析方法得到传感器低频噪声,通过传感器输入输出特性曲线得到其灵敏度和非线性等参数。利用该系统对商业化巨磁阻传感器AA002进行了测试,得到其在6 V供电时噪声平方根普密度约为槡10 nV/Hz(在10 kHz),线性范围内的灵敏度为3.35 mV/(G.V-1)。结果表明该系统为研究和分析磁阻型弱磁传感器的特性提供了一种有效的检测手段。

With the further investigation and extensive application of magnetoresistive（MR）weak magnetic field sensors,how expediently and quickly to measure the characteristics of sensors such as low frequency noise,sensitivity,nonlinearity,etc,has become the base for studying weak magnetic field detection ability.An automated testing system for characteristic parameters of MR sensors was designed and developed,whose noise square root spectrum density is less than 5 nV/Hz at 10 kHz.The hardware modular comprises Helmholtz coils,Wheatstone bridge,low-noise preamplifiers,mu-metal shields,high precision data acquisition card and PC.Low frequency noise of sensors was measured by cross-correlation power spectrum analysis technique and the sensitivity and nonlinearity of sensors were gained through the curves between input and output.The commercially available giant magnetoresistive sensor,GMR AA002,was tested with the system.Its noise square root spectrum density is 10 nV/Hz at 10 kHz supplied with 6 V voltage source,and its sensitivity is 3.35 mV/（G·V-1）in the linear range.The results have illustrated that the system is a valid detection instrument to study characteristics of MR sensors.