正确选择数据采集完整系统中英文翻译

1、Selecti ng the Right Data Acquisiti on SystemEngin eers ofte n must mon itor a han dful of sig nals over exte nded periods of time, and then graph and analyze the resulting data. The need to monitor, record and an alyze data arises in a wide range of applicati ons, in clud ing the desig n-verificati

2、 on stage of product development, environmental chamber monitoring, component in specti on, ben chtop testi ng and process trouble-shoot ing.This applicati on note describes the various methods and devices you can use to acquire, record and an alyze data, from the simple pen-an d-paper method to usi

3、ng todays sophisticated data acquisition systems. It discusses the advantages and disadva ntages of each method and provides a list of questi ons that will guide you in select ing the approach that best suits your n eeds.In troductio nIn geotechnical engineering, we sometime encounter some difficult

4、ies such as mon itori ng in strume nts distributed in a large area, dan gerous en vir onment of work ing site that cause some difficulty for easy access. In this case, operators may adopt remote control, by which a large amount of measureddata will be transmitted to a observati on room where the dat

5、a are to be collected, stored and processed.The automatic data acquisiti on con trol system is able to complete the tasks as regular automatic data mon itori ng, acquisiti on and store, featuri ng high automatio n, large data store capacity and reliable performa nee.The system is composed of acquisi

6、ti on con trol system and display system, with the followi ng features:1. No. of Chann els: 32 ( can be in creased or decreased accord ing to users real n eeds.)2. Scanning durati on: decided by user, fastest 32 poin ts/sec ond3. Store capacity: 20G( may be in creased or decreased)4. Display: (a) Ta

7、ble of parameter (b) History tendency (c) Colum n graphics.5. Fun cti on: real time mon itori ng con trol, warni ng6. Overall dimension: 50cm 50cmx72cmData acquisiti on systems, as the n ame implies, are products an d/or processes used to collect in formatio n to docume nt or an alyze some phe nomen

8、on. In the simplest form, a technician logging the temperature of an oven on a piece of paper is perform ing data acquisiti on. As tech no logy has progressed, this type of process has been simplified and made more accurate, versatile, and reliable through electronic equipment. Equipment ranges from

9、 simple recorders to sophisticated computer systems. Data acquisiti on products serve as a focal point in a system, tying together a wide variety of products, such as sensors that indicate temperature, flow, level, or pressure. Some com mon data acquisti on terms are show n below:Data acquisiti on t

10、ech no logy has take n gia nt leaps forward over the last 30 to 40 years. For example, 40 years ago, in a typical college lab, apparatus for track ing the temperature rise in a crucible of sodiumt un gste n- bronze con sisted of a thermocouple, a bridge, a lookup table, a pad of paper and a pen cil.

11、Todays college stude nts are much more likely to use an automated process and analyze the data on a PC Today, numerous options are available for gathering data. The optimal choice depe nds on several factors, i ncludi ng the complexity of the task, the speed and accuracy you require, and the documen

12、tation you want. Data acquisition systems range from the simple to the complex, with a range of performa nee and fun ctio nality.Pen cil and paperThe old pencil and paper approach is still viable for some situations, and it is inexpensive, readily available, quick and easy to get started. All you ne

13、ed to do is hook up a digital multimeter (DMM) and begi n recordi ng data by hand.Unfortun ately, this method is error-pr one, tends to be slow and requires exte nsive manual an alysis. In additi on, it works only for a sin gle cha nnel of data; while you can use multiple DMMs, the system will quick

14、ly becomes bulky and awkward. Accuracy is depe ndenton the tran scribers level of fastidious ness and you may n eed to scale in put manu ally. For example, if the DMM is not set up to han dle temperature sen sors, manual scali ng will be required. Taking these limitatio ns into acco unt, this is oft

15、e n an acceptable method whe n you n eed to perform a quick experime nt.Strip chart recorderModer n versi ons of the ven erable strip chart recorder allow you to capture data from several in puts. They provide a perma nent paper record of the data, and because this data is in graphical format, they

16、allow you to easily spot tren ds. Once set up, most recorders have sufficie nt internal in tellige nee to run un atte nded without the aid of either an operator or a computer. Drawbacks in clude a lack of flexibility and relatively low accuracy, which is ofte n con stra ined to a few perce ntage poi

17、n ts. You can typically perceive only small changes in the pen plots. While recorders perform well when mon itori ng a few cha nn els over a long period of time, their value can be limited. For example, they are un able to turn ano ther device on or off. Other concerns in clude pen and paper mainten

18、ance, paper supply and data storage, all of which translate into paper overuse and waste. Still, recorders are fairly easy to set up and operate, and offer a perma nent record of the data for quick and simple an alysis.Scanning digital multimeterSome ben chtop DMMs offer an opti onal sca nning capab

19、ility. A slot in the rear of the in strume nt accepts a sca nner card that can multiplex betwee n multiple in puts, with 8 to 10 cha nn els of mux being fairly com mon. DMM accuracy and the fun cti on ality in here nt in the in strume nts front panel are reta in ed. Flexibility is limited in that it

20、 is not possible to expa nd bey ond the nu mber of cha nn els available in the expa nsion slot. An exter nal PC usually han dles data acquisiti on and an alysis.PC plug-i n cardsPC plug-i n cards are sin gle-board measureme nt systems that take adva ntage of the ISA or PCI-bus expa nsion slots in a

21、PC. They ofte n have read ing rates as high as 100,000 read ings per sec ond. Counts of 8 to 16 cha nn els are com mon, and acquired data is stored directly into the computer, where it can the n be an alyzed. Because the card is essentially part of the computer, it is easy to set up tests. PC cards

22、also are relatively in expe nsive, in part, because they rely on the host PC to provide power, the mecha ni cal en closure and the user in terface.Data acquisiti on opti onsIn the dow nside, PC plug-i n cards ofte n have only 12 bits of resoluti on, so you cant perceive small variati ons with the in

23、 put sig nal. Furthermore, the electrical en vir onment in side a PC tends to be no isy, with high-speed clocks and bus no ise radiated throughout. Often, this electrical in terfere nee limits the accuracy of the PC plug-i n card to that of a han dheld DMM .These cards also measure a fairly limited

24、range of dc voltage. To measure other in put sig nals, such as ac voltage, temperature or resista nee, you may n eed some sort of exter nal sig nal con diti oning. Additi onal concerns include problematic calibration and overall system cost, especially if you n eed to purchase additi onal sig nal co

25、n diti oning accessories or a PC to accommodate the cards. Taking that into con siderati on, PC plug-i n cards offer an attractive approach to data acquisiti on if your requireme nts fall with in the capabilities and limitati ons of the card.Data loggersData loggers are typically sta nd-al one in st

26、rume nts that, once they are setup, can measure, record and display data without operator or computer in terve ntio n. They can han dle multiple in puts, in some in sta nces up to 120 cha nn els. Accuracy rivals that found in standalone bench DMMs, with performanee in the 22-bit, 0.004-percent accur

27、acy range. Some data loggers have the ability to scale measurements,check results aga inst user-defi ned limits, and output sig nals for con trol.One advantage of using data loggers is their built-in signal conditioning. Most are able to directly measure a nu mber of differe nt in puts without the n

28、 eed for additi onal sig nal con diti oning accessories. One cha nnel could be mon itori ng a thermocouple, ano ther a resistive temperature device (RTD) and still ano ther could be look ing at voltage.Thermocouple refere nee compe nsati on for accurate temperature measureme nt is typically built in

29、 to the multiplexer cards. A data loggers built-in in tellige nee helps you set up the test rout ine and specify the parameters of each cha nn el. Once you have completed the setup, data loggers can run as sta ndal one devices, much like a recorder.They store data locally in internal memory, which c

30、an accommodate 50,000 read ings or more.PC connectivity makes it easy to transfer data to your computer for in-depth analysis. Most data loggers are designed for flexibility and simple configuration and operati on, and many provide the opti on of remote site operati on via battery packs or other met

31、hods. Depending on the A/D converter technique used, certain data loggers take readings at a relatively slow rate, especially compared to many PC plug-i n cards. Still, readi ng speeds of 250 readi ngs/sec ond are not un com mon. Keep in mind that many of the phe nomena being mon itored are physical

32、 in n ature such as temperature, pressure and flow and cha nge at a fairly slow rate. Additi on ally, because of a data loggers superior measurement accuracy, multiple readings and averag ing are not n ecessary, as they ofte n are in PC plug-i n solutio ns.Data acquisiti on front endsData acquisiti

33、on front ends are ofte n modular and are typically conn ected to a PC or con troller. They are used in automated test applicati ons for gatheri ng data and for con trolli ng and rout ing sig nals in other parts of the test setup. Front end performa nee can be very high, with speed and accuracy rival

34、i ng the best sta ndal one in strume nts. Data acquisiti on front ends are impleme nted in a nu mber of formats, in clud ing VXI versi ons, such as the Agile nt E1419A multif un cti on measureme ntand con trol VXI module, and proprietary card cages. Although fron t-e nd cost has bee n decreas ing, t

35、hese systems can be fairly expe nsive, and uni ess you require the high performa nee they provide, you may find their price to be prohibitive. On the plus side, they do offer con siderable flexibility and measureme nt capability.Data Logger Applicati onsA good, low-cost data logger with moderate cha

36、 nnel count (20 - 60 cha nn els) and a relatively slow scan rate is more than sufficient for many of the applications engin eers com monly face. Some key applicatio ns in clude:? Product (haracterizatio n? Thermal profili ng of electro nic products? En viro nmen tai testi ng; en vir onmen tai mon it

37、ori ng? Comp onent characterizati on? Battery test ing? Build ing and computer room mon itori ng? Process monitoring, evaluation and troubleshooting No single data acquisition system works for all applicati ons. An sweri ng the followi ng questio ns may help you decide which will best meet your n ee

38、ds:1. Does the system match my applicati on?What is the measureme nt resoluti on, accuracy and no ise performa nee? How fast does it sca n? What tran sducers and measureme nt fun cti ons are supported? Is it upgradeable or expa ndable to meet future n eeds? How portable is it? Can it operate as a st

39、a ndal one in strume nt?2. How much does it cost?Is software in cluded, or is it extra? Does it require sig nal con diti oning add-ons? What is the warra nty period? How easy and in expe nsive is it to calibrate?3. How easy is it to use?Can the specificati ons be un derstood? What is the user in ter

40、face like? How difficult is it to rec on figure for new applicati ons? Can data be tran sferred easily to new applicati ons? Which applicati on packages are supported?Con clusi onData acquisition can range from pencil, paper and a measuring device, to a highly sophisticated system of hardware in str

41、ume ntati on and software an alysis tools. The first step for users contemplating the purchase of a data acquisition device or system is to determ ine the tasks at hand and the desired output, and the n select the type and scope of equipment that meets their criteria. All of the sophisticated equipm

42、e nt and an alysis tools that are available are desig ned to help users un dersta nd the phenomena they aremonitoring . The tools are merely a means to an end.正确选择数据采集系统工程师经常要对很长时间内的很多信号进行监测、画图和分析产生的数据。 监测、记录和分析数据在大范围内的应用趋势上升，包括设计-检定产品发展状态、环境的监测、组成物的检验、benchtop测试和处理故障检查。从简单的纸笔记录方法到现在所使用的复杂的数据采集系统这些应

43、用笔记描述 了你能获得、记录和分析数据的很多种不同方法和装置。讨论每一种方法的缺点 和优点，然后列出一张能够指引你选择适合你实际需要的问题单。前边在工程上，我们有时遇到一些困难，诸如监控设备分散在大范围内，危 险的工作环境很容易引发一些困难。在这种情况下，操作者可能采用视讯遥控， 通过大量检测数据传输到检测室，在那里收集、存储和处理数据。自动数据采集的控制系统能够完成很多任务， 像自动定时数据监测，数据采 集和存储，高度自动化为特色，大量数据存储能力和可靠功能。自动数据采集的控制系统和显示系统优如下特点：1多通路数：32 （根据使用者的需要增长或减少）2扫描持续时间：由使用者决定，最快一秒种扫

44、描 32点3存储容量：20G（可能增加或减少）4显示：（a）参数表（b）历史趋势 （c）专栏图表5功能：实时监测、控制和报警6 大体尺寸：50cmriX 50cmriX 72cm数据采集系统，正如名字所暗示的，是一种用来采集信息成文件或分析一些 现象的产品或过程。在最简单的形式中，技术人员将烤箱的温度记录在一张纸上 就是数据采集。随着技术的发展，通过电子设备，这个过程已经得到简化和变得 比较精确、多用途和可靠。设备从简单的存储器发展到复杂的电脑系统。数据采 集产品像聚焦点一样为系统服务，和一系列产品一起，诸如传感器显示温度、水 流、程度或者过程。数据采集技术在过去30到40年以来已经取得了很大

45、的飞跃。举例来说，在 40年以前,在一个著名的学院实验室中,为追踪用青铜做的坩埚中的温度上升情 况的装置是由热电偶、继电器、查询台、一捆纸和一支铅笔。今天的大学学生很可能在 PC机上自动处理和分析数据，有很多种可供你选 择的方法去采集数据。至于选择哪一种方法取决于多种因素，包括任务的复杂度、 你所需要的速度和精度、你想要的证据资料等等。无论是简单的还是复杂的，数 据采集系统都能够运行并发挥它的作用。铅笔和纸用铅笔和纸的旧方式对于一些情形仍然是可行的， 而且它便宜、易获得、快 速和容易开始。而你所需要的就是捕捉到多路数字信息 （DM）然后开始用手记 录数据。不幸的是这种方法容易发生错误、采集数据

46、变慢和需要太多的人工分析。 此 外，它只能单通道采集数据；但是当你使用多通道DMMt系统将很快变得非常 庞大和呆笨拙。精度取决于誊写器的水平，并且你可能需要自己动手依比例输入。 举例来说，如果DMM没有配备处理温度的传感器，旧需要动手找比例。考虑到这 些限制，只有当你需要实行一个快速实验时，它才是一个可接受的方法。长条图表记录仪现代多种版本的长条图表记录仪允许你从多个输入取得数据。他们提供数据 的长备纸记录，因为数据是图解的格式，他们易于现场采集数据。一旦建立了长条 图表记录仪，在没有操作员或计算机的情况下，大多数记录仪具有足够的内部智 能运行。缺点是缺乏灵活性和相对的精度低， 时常限制在百分

47、点。你能很清楚地 感觉到与笔只有小的改变。在多通道内较长时间的监控，记录仪能发挥很好的作 用，除此之外，它们的价值得到限制。举例来说，他们不能够与另外的装置轮流 作用。其他的顾虑就是笔和纸的维护，纸的供给和数据的存储，最重要的是纸的滥 用和浪费。然而，记录仪相当容易建立和操作，为数据快速而简单的分析提供永 久的记录。数字扫描传多用表一些ben chtop DMMs提供可选择的扫描能力。仪器的背面有一个槽孔接收 一张在较多输入时能多重发讯的扫描仪卡片，通常是8到10通道的mu。固有的在仪器的前面嵌板中的受到限制。 它的柔韧性也受到限制，因为它不能超过可 用通道数。外部的PC机通常处理数据采集和分

48、析。PC机插件卡片PC机插件卡片是单板测量系统，它利用ISA或PCI总线在PC机内扩大插槽。 它们时常具有高达每秒1000的阅读速率。8到16通道是普遍的，采集的数据直 接存储在电脑里，然后进行分析。因为卡片本质上是计算机的一部分 ，建立测试 是容易的。PC机卡也相对的便宜，一部分地，因为他们以来主机 PC去提供能源、 机械附件和使用界面。数据采集的选择在缺点上，PC机插件卡片时常只有12字的容量，因此你不能察觉输入信号 的小变化。此外，PC机内的电子环境经常很容易发出噪声、产生高速率的时钟和 总线噪声，电子接触面限制PC机插件卡片的精度。这些插件卡片也测量一定范 围的电压。为了测量其他输入信号，如电压、温度和阻力，你也许需