Eddy current displacement sensor with ultrahigh

resolution obtained through the noise suppression

of excitation voltage

GuoFeng Zhao, Jin Ying, Lei Wu, ZhiHua Feng.

Link: https://www.sciencedirect.com/science/article/pii/S0924424719301451

DIO:  10.1016/j.sna.2019.111622

Abstract

This paper presents a method for heightening the resolution of an eddy current sensor (ECS). A typical ECS based on AC bridge and orthogonal phase sensitive detector is used to explain the principle and is verified with experiments. For this type of ECS, the noise in the excitation voltage applied on the bridge is considered to have an important influence on the sensor’s resolution. A high-Q passive LC bandpass filter used for depressing the noise in the excitation voltage is designed and analyzed. Experimental results show that the sensor’s resolution is greatly improved with the help of the filter. With a working range of 20 μm and a bandwidth of 7.2 Hz, the sensor’s resolution is heightened from 0.35 nmrms to 0.05 nmrms.

文章摘要：

   本文提出了一种提高涡流传感器分辨率的方法。以一种典型的基于交流电桥和正交相敏检波器的电涡流传感器为例，阐述了其工作原理，并进行了实验验证。对于这种类型的涡流传感器，施加在电桥上的激励电压中的噪声被认为对传感器的分辨率有重要的影响。设计并分析了一种用于抑制激励电压噪声的高Q无源LC带通滤波器。实验结果表明，该滤波器大大提高了传感器样机的分辨率。在20μm量程和7.2Hz的带宽下,传感器的分辨率从0.35 nm提高到0.05nm。

图片摘要：

   在全量程范围内，在滤波和未滤波的情况下分别对传感器的分辨率进行了测试。可以看出,优化后传感器的分辨率达到了0.05nm,传感器的分辨率被提高了六倍。

意义与问题：

   很多传感器，不仅仅局限于电涡流传感器，工作时都有一个激励信号。这里的研究证明，信号对传感器的分辨率有很直接的影响。

   可以通过滤波器等措施改进信号的质量，大大提高传感器的分辨率。但需要注意的是，处理电路的引入，往往会带来稳定性变差的问题。

   为了解决稳定性问题，进一步提高传感器的性能，本实验室进行了更深入的研究。有关成果将发表在IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS上：

Ultrastable and low noise self-compensation method for circuit thermal drift of eddy current sensors based on analog multiplier