基于隧穿磁阻效应的宽频微小量程电流传感器设计及噪声分析

Design and Noise Analysis of Weak Current Sensor with Broadband Based on Tunneling Magnetoresistance Effect

针对电网中微弱电流的测量需求,研制了基于隧穿磁阻效应的百μA级无接触式微电流传感器,并对微电流传感器进行低噪声设计,包括电源模块、放大模块、调零和输出模块。测试了采用不同传感芯片传感器的微弱电流探测能力,其最小可测电流幅值为280μA,对应传感器的带宽达10 kHz。并对传感器系统各模块的噪声水平进行了测量分析与计算,结果表明隧穿磁阻芯片的1/f噪声(低频噪声)是限制传感器最小可测电流幅值的主要因素。该微电流传感器可以适应智能电网微弱电流测量需求。

According to the demands of measuring weak currents in smart grids,the contactless wideband weak current sensors with the amplitude of several hundredμA based on tunneling magnetoresistance(TMR)effect were studied.The weak current sensors were specially designed for lower noise,including power module,amplifier module,zero setting module,and output module.The various characteristics of the weak current sensors with different sensing chips were measured,which indicated that the minimum measurable amplitude could be as small as 280μA with a bandwidth of up to 10 kHz.After measuring and analyzing the noise levels of different modules of the sensor,it is concluded that the 1/f noise(low frequency noise)of the TMR chip is the main factor limiting the minimum measurable current value of a sensor.Overall,the proposed weak current sensors are adapted to the actual measurement requirements in smart grids.