Abstract: The counting machine mainly relies on magnetic safety line, magnetic ink, optical characteristics to identify counterfeit banknotes. Some counterfeit or old banknotes which stick transparent adhesive tapes with different sizes and positions should also be distinguished, but it’s difficult to identify them through existing technology. A multiple section mechanical thickness sensor is designed to convert the thickness of paper money into mechanical displacement, by using the precise displacement sensor based on the LDC1000 inductive digital converter provided by TI company to realize the positioning detection of the thickness of different parts of banknotes. Firstly, the structure and working principle of the mechanical thickness sensor are described. Then introduces the sensor circuit system that designed with the tool of WEBENCH ® Designer LDC1000 provided by TI company. The preliminary test results show that, the resolution of the sensor is better than 5μm in the range of 1 mm and the detection rate reaches 10kHz. The design meets the requirements of banknote thickness detection.

Key words: Eddy current, banknote, mechanical thickness sensor, inductance-to-digital converter

摘要： 点钞机主要依靠磁性安全线、磁性油墨、光学特征等特征来识别伪钞，部分伪钞或残旧钞票粘贴有大小、位置不同的透明胶纸也要区分，难以通过现有技术识别。设计了一种多段机械式厚度传感器，将纸币的厚度转化为机械位移，利用基于TI公司的LDC1000电感数字转换器组成的精密位移传感器实现纸币不同部位厚度的定位检测。首先阐述了机械式厚度传感器的结构与工作原理，并介绍采用TI公司提供的WEBENCH®Designer LDC1000工具设计传感器电路系统。初步试验结果表明，该传感器可在1 mm检测范围内达到优于5 μm的分辨率，检测速率达到10 kHz，满足纸币厚度检测要求。

关键词: 电涡流, 纸币, 厚度检测, 电感数字转换器, 鉴伪