作为PLC攻城狮当然要回答一个根本的问题: 什么是PLC? 
可编程逻辑控制器(Programmable Logic Controller,简称PLC),一种具有微处理器的数字电子设备,用于自动化控制的数字逻辑控制器,可以将控制指令随时加载存储器内存储与运行。可编程控制器由内部CPU,指令及数据存储器、输入输出单元、电源模块、数字模拟等单元所模块化组合成。PLC可接收(输入)及发送(输出)多种类型的电气或电子信号,并使用他们来控制或监督几乎所有种类的机械与电气系统。  siemens的PLC
国际电工委员会(IEC)在其标准中将PLC定义为: 可编程逻辑控制器是一种数字运算操作的电子系统,专为在工业环境应用而设计的。它采用一类可编程的存储器,用于其内部存储程序,执行逻辑运算、顺序控制、定时、计数与算术操作等面向用户的指令,并通过数字或模拟式输入/输出控制各种类型的机械或生产过程。可编程逻辑控制器及其有关外部设备,都按易于与工业控制系统联成一个整体,易于扩充其功能的原则设计。 美国通用汽车公司在1968年提出了著名的“通用十条”招标指标,也是当前PLC的特点: - 编程方便,现场可修改程序;
- 维修方便,采用模块化结构;
- 可靠性高于继电器控制设备;
- 体积小于继电器控制设备;
- 数据可直接送入计算机;
- 成本可与继电器控制设备竞争;
- 输入可以是交流115V;
- 输出为交流115V,2A以上,能直接驱动电磁阀,接触器等;
- 在扩展时,原系统只要很小变更;用户程序存储器容量能扩展。
1978年美国电机制造协会(NEMA)对可编程控制器定义是: 可编程控制器是一种以数字动作之电子设备,它使用可编程存储器以存储指令,运行像是逻辑、顺序、计时、计数与演算等功能,并透过数字或模拟输入输出模块,控制各种的机械或工作程序。 PLC具有通用性强、使用方便、适应面广、可靠性高、抗干扰能力强、编程简单等特点。 http://www.sina.com.cn/mid/search.shtml?q=%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%851321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%851321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E6%AC%A7%E4%BA%9A%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%9A%87%E5%AE%B6%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%9A%87%E5%AE%B6%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%851321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%9A%87%E5%AE%B6%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%9A%87%E5%AE%B6%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%9A%87%E5%AE%B6%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%851321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E9%93%B6%E6%B2%B3%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E9%93%B6%E6%B2%B3%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E9%93%B6%E6%B2%B3%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E9%93%B6%E6%B2%B3%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E9%93%B6%E6%B2%B3%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E8%B4%A2%E7%A5%9E%E5%9B%BD%E9%99%851321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E8%B4%A2%E7%A5%9E%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E8%B4%A2%E7%A5%9E%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E8%B4%A2%E7%A5%9E%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E8%B4%A2%E7%A5%9E%E5%9B%BD%E9%99%85%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E8%B4%A2%E7%A5%9E%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E8%B4%A2%E7%A5%9E%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E8%B4%A2%E7%A5%9E%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E8%B4%A2%E7%A5%9E%E5%9B%BD%E9%99%85%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%BB%B4%E5%8A%A0%E6%96%AF%E8%B5%8C%E5%9C%BA1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E7%BC%85%E7%94%B8%E7%BB%B4%E5%8A%A0%E6%96%AF%E8%B5%8C%E5%9C%BA%E5%AE%A2%E6%9C%8D1321l832221 http://www.sina.com.cn/mid/search.shtml?q=%E5%B0%8F%E5%8B%90%E6%8B%89%E7%BB%B4%E5%8A%A0%E6%96%AF1321l832221
|