问题
问答题 简答题
简述可编程控制器工作的特点？
答案
参考答案：
PLC的工作的工作过程是周期循环扫描的：E作过程，以满足生产过程实时控制的需要；PLC在一个扫描周期里分三个阶段即：输入采样、程序执行、输出刷新，由样集中采样、集中输出的工作方式，减少了外界干扰的影响
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简述可编程控制器工作的特点？
参考答案：
PLC的工作的工作过程是周期循环扫描的：E作过程，以满足生产过程实时控制的需要；PLC在一个扫描周期里分三个阶段即：输入采样、程序执行、输出刷新，由样集中采样、集中输出的工作方式，减少了外界干扰的影响
Thousands of years ago, people didn't live in cold places because they didn't know how to keep themselves warm. Later they learned to make clothes. When an animal was killed, they made use of its skins to cover their bodies. 小题1: .
小题2: . It once helped people find fire, when lighting hit a forest and started a fire. 小题3: The fire kept them warm, and also frightened wild animals. Soon people found the food cooked tasted much better, so they began to use the fire to cook food.
But people still didn't know how to make a fire. When they got a fire from the forest they tried to keep it burning. 小题4:
But later they found different ways to make fire. For example, they made fire by burning wood or knocking two pieces of stones.
Today it's easy for people to make fire because they have matches, lighters and different kinds of heaters. 小题5:
根据短文内容，把A-E五个选项填入文中空缺处，使短文内容完整、正确。
| A. If it went out, they had to wait for years. B. The skins keep them warm. C. They can make fire at any time they need. D. People took some of this fire to their homes. E. Nature is people's good friend.. |