Question

自动化专业英语在线翻译

From a history point of view ，flow measurement started long ago. Ancient Egyptians used weirs to measure irrigation water。Later on ，the Romans used the orifice plate to measure the water supply to household 。the technology has evolved to the point where highly accurate and reliable devices are now on the market 。new measurement principles are being introduced ，and existing principles are continuously improved upon。
Flow measurement is a key parameter used for reading values（including accounting needs）and for control。Of the typical measurement of flow，level，temperature，and pressure；flow tends to be the most difficult and therefore the most subject to incorrect device selection。
As a starting point，it should be mentioned that no single flow meter can cover all flow measurement applications 。Flow meter selection has been to as a science and an art。
An important construction of feedback control is that it can cause oscillatory responses.
If the oscillation has a small amplitude and damps out quickly ， then the control system performance is generally considered to be satisfactory.
however ，under certain circumstances the oscillation may be undamped or even have a amplitude that increases with time until a physical limit isreached ，such as a control valve being fully open or completely shut . In these situations ，the closed-loop system is said to be unstable .
In this unit we analyze the stability characteristics of closed-loop system
And present several useful criticeria for determining whether a system will be stable . additional stability base on frequency response analysis are not discussed here . But first we consider an illustrative example of a closed-loop system that can become unstable

Answer 1

从历史的角度来看,流量测量的开始。古代埃及人用堰测量水位.然后,罗马人用节流板来衡量,供水技术已经发展成为家庭的高度准确、可靠的设备是目前市场上被引入新的测量原理,现有的原则是不断的改进。
流量测量的关键参数用于读值(包括会计的需要),为了便于控制.典型计量流量、压力、温度、水平;流动趋近于最困难和最受不正确的设备选型。
作为一个起始点,应当指出,没有一种单一的流量仪表可以覆盖所有的流量测量的应用.Flow仪表选型已经成为一门科学和艺术

一个重要的建筑,就是能回馈控制引起振动响应。
如果有一个小振幅、振动会遏制了快,然后控制系统的性能通常被认为是令人满意的。
然而,在某些情况下的振动可能都有一种甚至无阻尼自由振动微分振幅随时间的增加,直到身体极限的分裂,如控制阀全开或者完全关闭。在这种情况下,使得闭环系统是稳定的。
在本单元中,我们分析了闭环系统稳定性特征
目前,criticeria有用的几个判定系统才会稳定。另外稳定性分析的基础上进行频率响应是没有在这里。但首先我们考虑一个数值例子的闭环系统,该系统能变得不稳定

Answer 2

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