基于巨磁阻传感器的无损检测系统研究与设计

Design of giant magneto-resistive(GMR) sensor-based non-destructive testing system

针对现代工业与安全检测中对非铁磁性工件的表面及近表面缺陷检测需要,基于涡流无损检测原理,采用灵敏度高、体积小、工作频率范围宽(0Hz到MHz)的GMR传感器,结合基于单片机STM32的直接数字频率合成(DDS)信号产生方法及锁相技术研制了一套涡流无损检测系统。实验结果表明该基于GMR传感器的无损检测系统能够较好的检测出铝板试件表面及表面下2mm处缺陷的存在,多道扫描结果可清晰判别出缺陷的位置和大小,该系统可以准确完成对导电材料表面及近表面的无损检测。

For the need of modern industrial safety testing of surface and near-surface defect detection of non-ferromagnetic workpieces,based on the principle of eddy current testing and the giant magneto-resistive（GMR）sensors,Nondestructive Testing method is an effective eddy current testing technique which has a lot of advantages such as the high sensitivity,high resolution,wide operating frequency range（0Hz to MHz）,small sensor volume and simple signal processing circuit and easy integration.In this paper,one simple and excellent GMR-based eddy current system is designed.The GMR sensor with high sensitivity of 30mv/Oe,the microcontroller STM32-based direct digital synthesis signal generation method and phase-lock technique are used in this system.The results show that the GMR-based eddy current system can detect the presence of the defective on the surface or under the aluminum plate surface 2mm,the shape and location can be known by multi-channel scanning.The system can accurately perform non-destructive testing of surface or near-surface defect detection for nonmagnetic metals.