磁探针速度传感器研究

STUDY ON MAGNETIC NEEDLES AS VELOCITY GAUGES

应用Hopkinson杆装置,对磁探针速度计进行了实验测定。发现对待测自由面速度阶跃,磁探针有两种类型稳定的输出信号,分别对应于不同的速度范围。对某个特定磁探针来说,其初始信号峰值与速度成正比的条件是速度大于某个阈值。实验还测定了间距大小对磁探针输出信号的影响,给出了磁探针对阶跃实验的响应波形。基于实验条件,本文探讨了磁探针原理、测量电路特性以及靶板涡流的穿透深度等理论问题,得到的结果可以定性解释磁探针的两种特征信号以及它们间的转化机理。本文工作表明,磁探针可以用来定量测量自由面速度的初始阶跃幅度,准确测定全时域的速度阶跃时刻,但不足以确定整个速度历史。为使这种传感器更加成熟,其结构和线路有待改进。

By using of Hopkinson bar apparatus, the magnetic needles were studied experimentally as velocity gauges. It was found that there were two types of signal profiles carres ponding to different velocity ranges. For a typical magnetic needle,the initial signal peak became proportional to the velocity step after a threshold value of velocity was over taken. The influence of the crevice width to the gauge output was also tested,the response of jump test was obtained. Based on our experiments,the gauge principle,the circuit characteristics and the skin depth of the eddy-current were analyzed,a set of analytical formula were obtained that could illustrate the experimental phenomena qualitatively. Our results show that this kind of velocity gauges can be used to measure the initial velocity jumps of a free surface,and the times of velocity jumps in the whole process,but they are unable to obtain a quantitative velocity profile in a whole process. Further improvements are needed for this technique.