问题 问答题 简答题

什么是一次仪表?什么是二次仪表?

答案

参考答案:一次仪表就是现场安装仪表,主要为测量变送单元和执行单元两类。一次仪表传输信号为4~20mA直流电流,由24V直流电源箱统一供电。

包括:①变送单元类②执行单元类

二次仪表就是控制室内安装仪表,主要为转换单元类、调节单元类、运算单元类、显示单元类、给定单元类和辅助单元类。二次仪表之间运输信号为1~5V直流电压,由24V直流电源箱统一供电。

包括:①转换单元类②调节单元类

③运算单元类④显示单元类

⑤给定单元类⑥辅助单元类

多项选择题
阅读理解

阅读理解。

     A year ago, I paid no attention to English idioms, though my teacher emphasized (强调) the importance again and again. But soon, the importance of English idioms was shown in an amusing experience.

     One day, I happened to meet an Englishman on the road, and soon we began to talk. As I was talking about how I was studying English, the foreigner seemed to be astonished. Gently shaking his head,

shrugging his shoulders, he said, "You don't say!" "You don't say!" I was puzzled. I thought, perhaps this is not an appropriate topic (适当的话题). "Well, I'd better change the topic." So I said to him. "Well, shall we talk about the Great Wall? By the way, have you ever been there?" "Certainly, everyone back home

will laugh at me if I leave China without seeing it. It was magnificent." He was deep in thought when I

began to talk like a tourist guide. "The Great Wall is one of the wonders in the world. We are very proud

of it." Soon I was interrupted again by his words:"You don't say!" I couldn't help asking, "Why do you ask me not to talk about it?" "Well, I didn't request you to do so, " he answered, greatly surprised. I said, "

Didn't you say' you don't say?" Hearing this, the Englishman laughed to tears. He began to explain, 'You

don't say' actually means 'really!' It is an expression of surprise. Perhaps you don't pay attention to English

idioms." Only then did I know I had made a fool of myself. Since then I have been more careful with

idiomatic expressions. Remember: what the English teachers said is always right to us students.

1. A year ago, I paid no attention to English idioms because _______.

A. English idioms were not important  

B. I was not careful with English idioms

C. my teacher didn't emphasize the importance of them  

D. I had no interest in them

2. At first, on hearing "You don't say," I thought the foreigner meant _______.

A. he was not interested in the topic  

B. he was only interested in the Great Wall

C. I had talked too much            

D. I had to stop talking

3. The underlined word in the first paragraph probably means _______.

A. interesting

B. important

C. terrible

D. unlucky

4. Which of the following is true according to the passage?

A. The Englishman left China without seeing the Great Wall.

B. The Englishman wanted to see the Great Wall after I talked about it.

C. The Englishman wanted me to act as his guide.

D. The Englishman visited the Great Wall and thought it worth visiting.

5. After the Englishman explained the idiom, _______.

A. I thought the Englishman had made me a fool  

B. the Englishman became a real fool.

C. I felt very silly          

D. I became more carefully in everything