A simple sensor design to achieve different electromechanical impedance (EMI) characteristics is required for the serial/parallel multi-sensing interrogation. Aiming at the shortcomings of traditional trial-and-error method for collocating serial/parallel PZT transducer with different EMI characteristics, this paper proposes a simple but effective method to design and fabricate PZT transducers with distinguished EMI characteristics by bonding PZT patch on permanent magnet disks with different thickness. The thickness of the magnetic disk could change the impedance resonant frequency of the transducer almost linearly, which greatly simplifies the transducer design to ensure each one has distinguished peak frequency. The EMI responses of proposed smart modulation transducer (SMT) under different thickness of magnetic disk were obtained by finite element method (FEM) simulations, as well as by experiments. The simulation outcomes are in good agreement with experimental results. And it is concluded that the EMI resonant peak frequency of SMT increases linearly due to the increase of magnet thickness, which ensures each SMT has very different EMI characteristics. Both experiments and simulations have confirmed that the proposed method is effective. To obtain the insight of the performance of the SMT to structural damage detection using multi-sensing EMI method, the four fabricated SMTs with different thickness of magnetic disk were series-connected for multi-bolt loosening monitoring. Results validate that the response signatures with distinguished EMI characteristics can be obtained, and both the severity and location of bolt looseness can be identified via the modified MAPD (mean absolute percentage deviation) damage index. The proposed PZT design method has great guiding role for optimizing the design of sensors for EMI-based multi-sensing interrogation, promoting the practical application of EMI technology in metal structure health monitoring.

串行/并行多传感查询需要一种简单的传感器设计来实现不同的机电阻抗（EMI）特性。针对传统的试错法并置不同EMI特性的串联/并联PZT换能器的缺点，提出了一种简单有效的方法，通过将PZT贴片粘结在永磁磁盘上来设计和制造具有EMI特性的PZT换能器。具有不同的厚度。磁盘的厚度可以几乎线性地改变换能器的阻抗谐振频率，这大大简化了换能器的设计，以确保每个换能器具有不同的峰值频率。通过有限元（FEM）仿真以及实验，获得了所建议的智能调制换能器（SMT）在不同磁盘厚度下的EMI响应。仿真结果与实验结果非常吻合。可以得出结论，由于磁体厚度的增加，SMT的EMI谐振峰值频率呈线性增加，这确保了每个SMT的EMI特性都有很大的不同。实验和仿真都证实了该方法是有效的。为了了解SMT在使用多感应EMI方法检测结构损伤方面的性能，将四个具有不同磁盘厚度的SMT串联连接以进行多螺栓松动监测。结果证实，可以获得具有出色的EMI特性的响应特征，并且可以通过修改后的MAPD（平均绝对百分比偏差）损坏指数来识别螺栓松动的严重程度和位置。提出的PZT设计方法对于优化基于EMI的多传感器询问传感器的设计具有重要的指导作用，促进了EMI技术在金属结构健康监测中的实际应用。