毕业论文-基于单片机的二线制数据传感器设计.doc

摘 要 工业上普遍需要测量各类非电物理量，例如温度、压力、速度、角度等。都需要转换成模拟量电信号才能传输到几百米外的控制室或显示设备上，这种将物理量转换成点信号的设备称为变送器。工业上最广泛采用的是用4~20mA电流来传输模拟量。 采用电流信号的原因是不容易受到干扰，并且电流源内阻无穷打，导线电阻串联在回路中不影响精度，在普通双绞线上可以传输数百米。取20mA是因为防爆的要求，20mA的电流通断引起的火花能量不足引燃瓦斯；下限没有取0mA的原因是为了能检测断线，正常工作时不会低于4mA，当传输线因故障断路，环路电流降为0mA所以常取2mA作为断线报警值。 本课题通过分析二线制、三线制、四线制变送器的各自特点，在总结典型变送器设计思路与方法的基础上，提出了一张经济实用的二线制智能变送器设计方案。该方案单片机为核心，能对特殊的非线性的传感器进行线性修正处理。主要解决问题是两条线既要提供工作电流，又要传输测量信号，需要协调一致，不能相互冲突；由于零点电流为4mA，因此必须保证整个变送器的工作电流要在3.5mA之内；线制的输出电流反馈电路比较特殊，要选择合理的电路方案，保证输出电流即工作电流不随负载与工作电压变化而变化。 关键词 ：两线制变送器 V/I变换电路 调理电路 单片机  Abstract Industry generally need to measure all kinds of non-electric physical quantity, such as temperature, pressure, speed, Angle and so on. Needs to be converted into analog electrical signals can transmit to hundreds of meters outside of the control room or display device, the convert quantity into point signal device called a transducer. Industry is the most widely used to transmit analog 4 ~ 20 ma current. Adopt the cause of the current signal is not easily disturbed, and infinite, current source internal resistance wire resistance in series in the circuit will not affect the accuracy. Sad take 20 ma because explosion-proof requirements, 20 ma electric current caused by broken spark ignition gas energy shortage; Floor didnt take 0 ma in order to detection of bolt, is the cause of not less than 4 ma in normal working conditions, when the transmission line circuit because of malfunction, the loop current is reduced to. Often take 2 ma as a disconnection alarm value. This topic by analyzing the two wire, three wire system and four wire transducer characteristics, summarizing the typical transducer, on the basis of design idea and method, put forward a two wire system intelligent transmitter design scheme of economical and practical. To a single chip microcomputer as the core, special nonlinear sensor linear correction processing. Due to the zero current is 4 mA, so must ensure that the transducer working current to withi