Research on Synchronous Excitation and Detection Method for Synthetic Multi-frequency Magnetic Induction Signals
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摘要: 磁感应检测技术是一种非接触、无创的电阻抗检测技术,多频率同步检测可同时获得不同频率下被测对象的阻抗信息。该文首先研究了磁感应信号多频率同步激励与检测原理,基于Walsh函数合成了5频率激励信号。其次分析了合成多频率同步检测性能,设计了合成多频磁感应信号同步检测系统。最后,通过合成5频率激励信号与同步检测系统进行不同电导率NaCl溶液的检测实验,结果表明:合成5频率激励信号5个主谐波的测量结果都具有很好的线性度,为磁感应信号多频率同步检测提供了激励-检测方法。Abstract: Magnetic induction detection technology is a non-contact and non-invasive electrical impedance detection technology. Multi-frequency synchronous detection can simultaneously obtain the impedance information of the tested object at different frequencies. Firstly, the principle of multi-frequency synchronous excitation and detection of magnetic induction signal are studied. Five-frequency excitation signal is synthesized based on Walsh function. Secondly, the performance of synthesized multi-frequency synchronous detection is analyzed, and a synthesized multi-frequency magnetic induction signal synchronous detection system is designed. Finally, the detection experiments of NaCl solution with different conductivities are carried out by synthesizing five-frequency excitation signal and synchronous detection system. The results show that the measurement results of five main harmonics of synthesized five-frequency excitation signal have good linearity. It provides an excitation-detection method for multi-frequency synchronous detection of magnetic induction signal.
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表 1 合成5频率同步信号f(5, t)的主谐波Hk频谱特性
Hk f0 2f0 4f0 8f0 16f0 总和 bk(V) 0.6173 0.5882 0.5443 0.4775 0.4775 Pk(%) 19.05 17.30 14.76 11.40 11.40 73.91 表 2 合成5频率激励信号f(5, t)的主谐波Hk频率值
Hk f0 2f0 4f0 8f0 16f0 Tclk=100 μs 312.5 Hz 625 Hz 1.25 kHz 2.5 kHz 5 kHz Tclk=50 μs 625 Hz 1.25 kHz 2.5 kHz 5 kHz 10 kHz 表 3 电导率与NaCl溶液浓度关系表
电导率$\sigma $(S/m) 1.0 2.0 3.0 4.0 ppm(mg/L) 5439 11476 17624 23713 表 4 不同电导率NaCl溶液同步检测结果
$\Delta {b_k}$(mV) f0 2f0 4f0 8f0 16f0 1.0 S/m 265.355 252.738 233.404 205.126 205.396 2.0 S/m 277.931 264.274 244.421 214.596 214.693 3.0 S/m 290.190 276.316 255.436 224.515 224.252 4.0 S/m 302.210 288.198 266.145 233.576 234.086 表 5 各谐波归一化系数
Hk f0 2f0 4f0 8f0 16f0 归一化系数 1.000 1.050 1.136 1.293 1.293 表 6 归一化处理后不同电导率NaCl溶液同步检测结果
$\Delta {b_k}$(mV) f0 2f0 4f0 8f0 16f0 平均值 1.0 S/m 265.355 265.269 265.160 265.210 265.560 265.311 2.0 S/m 277.931 277.377 277.677 277.454 277.579 277.603 3.0 S/m 290.190 290.016 290.190 290.279 289.939 290.123 4.0 S/m 302.210 302.487 302.356 301.993 302.653 302.340 -
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