摘要温度、液位在供液系统中是两个非常重要的物理量。在日常生活和工业生产中，无论是实时准确地获取这两者的数值还是目的性地控制其大小，都是非常关键的应用技术。传统的温度控制精度不够高，速度不够快。如接触器温度控制仪表配合使用控制接触器，它的主要工作原理是通过通断时间的调整改变加热功率，但考虑到器件的误差和寿命等因素影响效果不佳。而在传统的液位控制中，水泵的运行是固定的，这意着能耗很大。在工业蓬勃发展的当今，高精准、高效节能成为评判一个产品的重要指标。利用PLC配合PID算法搭建需要的系统可以满足这些要求。46442
本文介绍用西门子S7-200PLC、触摸屏、温度传感器、液位传感器、模拟量控制模块、周波控制器和固态继电器、电加热器、变频器、水泵等控制储水箱液体温度、液位的电气控制系统的设计，实现温度、液位在触摸屏上的显示以及恒温、恒液位控制功能。
毕业论文关键词：PLC；恒温；恒液位；控制系统；
ABSTRACT
The temperature and liquid level in the liquid supply system are two kinds of important physical quantity. In daily life and industrial production, it is very important to obtain both the numerical value of the two and controlling the size of the object in real time. The traditional temperature control precision is not high and the speed is not fast. Such as the contactor temperature control instrument with the use of the relay contactor control. Its main working principle is through the on-off time to adjust to the change the heating power, but taking into account the device error and life factors such as the effect is poor. In the traditional level control, the operation of the pump is fixed, which means that the energy consumption is very large. Nowadays, with the rapid development of industry, high precision, high efficiency and energy saving has become an important index to judge a product. Using PLC to meet the requirements of the system can meet the requirements of the PID algorithm.
With Siemens S7-200 PLC, touch screen, a temperature sensor, liquid level sensor, analog control module, frequency controller and solid state relay, electric heaters, converter，water pump and other control the storage tank liquid temperature and liquid level of electrical controlling system design, to achieve the temperature and level in HMI and constant temperature and constant liquid level control function is presented in this paper.
Key words：PLC; Constant temperature; constant liquid level; controlling system；
目  录
第一章  绪论    1
1.1课题研究的背景    1
1.2课题研究的意义    1
1.3课题研究重要技术介绍    1
1.3.1传感器与检测技术    1
1.3.2 可编程逻辑控制PLC    2
1.3.3组态    2
第二章  硬件设计    3
2.1系统总体设计    3
2.1.1各模块包含器件及具体应用简要说明    3
2.2硬件接线图    4
2.3硬件配置    5
2.3.1西门子S7-200 CPU226    5
2.2.2传感器    5
2.2.3模拟量控制模块    7
2.2.4周波控制器    10
2.2.5固态继电器    11
2.2.6 MM440变频器    12
第三章  软件设计    15
3.1 PID控制程序设计    15
3.1.1 PID控制算法    15
3.1.2 PID回路指令    16
3.1.3回路输入输出变量的数值转换方法    17
3.1.4 PID参数整定    18
3.2程序设计流程图及基本组件    19 西门子S7-200PLC恒温恒液位控制系统设计+梯形图:http://www.751com.cn/zidonghua/lunwen_48151.html