运算放大电路在金属识别中的运用

Application of Arithmetic Amplification Circuits in Metal Identification

摘要: 在金属识别领域，电涡流传感器有着重要的地位，通过电磁感应的基本原理，对于不同的金属种类有着不同的输出特性。在实际使用过程中，直接使用电涡流传感器对金属进行识别，发现不同金属之间的差异较小，导致识别能力较低。本文主要研究通过运算放大电路将微小的变化进行放大，由于运算放大电路为反向放大，因此通过直流偏置技术将输出电压进行向上平移。采用单片机ADC + DMA功能，多次读取运算放大的输出电压，并通过软件进行滤波处理，获得测量值，将传感器负载状态下ADC值与空载下ADC值作差，结果视为待测金属特征值。对比添加运算放大电路前后，铁与铜样本之间的金属特征值差异出现了明显的放大。由此可见，运算放大电路的添加，可提高金属识别的准确率。

Abstract: In the field of metal identification, eddy current sensors play an important role, and through the basic principle of electromagnetic induction, they have different output characteristics for different metal types. In the actual use process, the eddy current sensor is directly used to identify the metal, and it is found that the difference between different metals is small, resulting in low identification ability. In this paper, the output voltage is shifted upwards by DC bias technology because the amplification circuit is reversed. Using the single-chip microcomputer ADC + DMA function, the output voltage of the amplification is read and calculated many times, and filtered by the software to obtain the measured value, and the ADC value under the load state of the sensor is compared with the ADC value under no load, and the result is regarded as the characteristic value of the metal to be measured. Compared with the amplification circuit before and after the addition of the amplification circuit, the difference in metal eigenvalues between the iron and copper samples is significantly amplified. It can be seen that the addition of arithmetic amplification circuit can improve the accuracy of metal identification.