【作者】 罗元国；

【导师】 黄志尧； 王保良；

【作者基本信息】 浙江大学 ， 检测技术与自动化装置， 2007， 硕士

【摘要】 电磁流量计是依据法拉第电磁感应定律的工作原理来测量流体体积流量的仪表,因其结构简单、无压损、测量范围大,是目前最常用的流量测量仪表之一。电容式电磁流量计是一种相对新型且仍在发展的电磁流量计,可以测量低电导率流体、泥浆混入型流体、附着型流体等使用传统电极式电磁流量计难以测量的流体,拓展了电磁流量计的适用范围,是近年来在电磁流量计研究领域的一个重要方向。本文在大量阅读相关文献的基础上,对电容式电磁流量计的传感器和信号转换电路等核心部分进行了研究,研制成功了一套样机系统,并在实验装置上通过了实验测试。本学位论文的主要贡献和研究工作有:(1)将相关检测理论引入信号转换器的设计中,利用旋转电容滤波技术提出了一种在低信噪比的情况下,如何将微弱的流量信号从强噪声背景中检出的新方法;(2)针对滤波输出的交流方波信号研制了整流采样电路,实验结果表明,该电路具有很强的干扰抑制能力,提供了一种稳定输出信号电压的方法:(3)研制了一套样机系统,并在实验装置上通过了实验测试,结果表明提出的方法是有效的,研制的样机是成功的。更多还原

【Abstract】 Electromagnetic flowmeter is a volumetric flowrate flowmeter which based on the Faraday’s law of induction. Due to its simple structure, no pressure loss and wide measurement range, electromagnetic flowmeter becomes one of the most popular flowmeters in industry. Capacitively-coupled electromagnetic flowmeter is a relatively new electromagnetic flowmeter and is still in developing. The capacitively-coulped electromagnetic flowmeter can measure low-conductivity fluids, high-concentration slurry fluids and adhesive fluids, which are difficult to be measured by the conventional electromagnetic flowmeters. Thus the capacitively-coupled electromagnetic flowmeter extends the application of electromagnetic flowmeter and become one of the important research content of the electromagnetic flowmeter in recent years.After reviewing the related literatures, research in this work focuses on the sensor and signal conversion circuit (the key parts of the capacitively-coupled electromagnetic flowmeter). A prototype flowmeter is developed and has been tested on the flow loop in lab. The main works are listed as follows:(1) The cross-correlation detection theory is introduced to the design of the signal converter and the rotating capacitor filter technology is applied to solve the problem of detecting the weak flow-related signal from the background with high level noise under the low signal-to-noise ratio condition.(2) For processing the signal come from the rotating capacitor filter, a synchronous rectification and sampling circuit is designed. Experimental results indicated that the circuit can reduce the noise and provide steady voltage signal.(3) A prototype of the capacitively-coupled electromagnetic flowmeter is developed and the measurement test is carried out on the experimental system. Experimental results indicated that the method is effective and the design of the prototype is applicable.更多还原