问题 问答题 简答题

某台往复式压缩机的出口压力范围为25.5~28.6MPa,测量误差不得大于1.OMPa。工艺上要求就地观察,并能高低限报警,试正确选用一台压力表,指出型号、精度与测量范围。

答案

参考答案:由于往复式压缩机的出口压力脉冲较大,所以选择仪表的上限值为P1=Pmax×2=28.6×2=57.2(MPa),根据就地观察及能进行高低限报警的要求,选用电接点压力表,型号为YX-150型。测量范围O~60MPa,由于25.5/60>1/3,故补测压力的最小值不低于满量程l/3,这是允许的。允许误差为1/60×100%=1.67%,选精度等级为1.5级的压力表能满足误差要求。所以,选择的仪表为YX-150型电接点压力表,测量范围为0~60MPa,精度等级为1.5级。

阅读理解

阅读理解。

      Modern life is impossible without traveling. The fastest way to travel is by air. With a modern

plane you can travel in one day to places which took a month or more one hundred years ago.

     Traveling by train is slower than by air, but it has its advantages. You can see the country you

are traveling in. Modern trains have comfortable seats and dining cars. They make even the longest

journey enjoyable.

     Some people prefer to travel by sea when it is possible. There are large liners and river boats

with which you can visit many other countries and different places. Traveling by sea is a very pleasant

way to spend a holiday.

     Many people like to travel by car. You can make your own timetable. You can travel three or four

hundred miles or only fifty miles a day, just as you like .You can stop wherever you wish: where there

is something interesting to see, at a good restaurant where you can enjoy a good meal, or a hotel to

spend the night. That is why traveling by car is popular for pleasure trips, while people usually take

a train or a plane when they are traveling on business.

1. From the passage we know that the fastest way to travel is ______

A. by car    

B. by train    

C. by plane      

D. by boat

2. If we travel by car, we can____________     .

A. only stop at the destination              

B. make our own timetable

C. travel to a very far place in several minutes  

D. travel one thousand miles a day.

3. The best title of this passage is___________________  .

A. ways to travel        

B. travels    

C. transportation      

D. modern life

4. How many ways to travel are mentioned in the passage?

A. Five    

B. Six      

C. Three        

D. Four

单项选择题