【導(dǎo)讀】diagram.verysimilar.

　　

【正文】 textbased languages, you must explicitly create and manage threads to implement parallelism, a major challenge for nonexpert programmers. In contrast, the parallel nature of G code makes multitasking and multithreading simple to implement. The builtin piler continually works in the background to identify parallel sections of code. Whenever G code has a branch in a wire, or a parallel sequence of nodes on the diagram, the piler tries to execute the code in parallel within a set of threads that LabVIEW manages automatically. In puter science terms, this is called “implicit parallelism” because you do not have to specifically write code with the purpose of running it in parallel。 the G language takes care of parallelism on its own. Beyond multithreading on a multicore system, G can provide even greater parallel execution by extending graphical programming to fieldprogrammable gate arrays (FPGAs). FPGAs are reprogrammable silicon chips that are massively parallel – with each independent processing task assigned to a dedicated section of the chip – but they are not limited by the number of processing cores available. As a result, the performance of one part of the application is not adversely affected when more processing is added. 6． Hardware Integration with NI LabVIEW (1)ave Development Time with Simpler System Integration Most measurement and control hardware es with software. Usually, that software only works with the device or devices similar to the one the software came with, and the software likely has a fixed, limited feature set. When you want to do more than you can with the included software, such as incorporate multiple devices or add processing and reporting, you face the often daunting task of getting the hardware to work in a different software environment. 11 System integration, getting everything setup and configured such that you begin programming a system, can be a major undertaking, often taking more time than the programming, measurement, or test you wish to perform. Integrating different hardware devices with traditional tools is littered with timewasting steps and possible inpatibilities, increasing risk. First, you have to find the correct drivers for all of your hardware, and then you have to figure out how to install them and call them from software. Once your drivers are usable, you need them to municate with the hardware and learn the programming model that the driver designer decided was appropriate for that particular device. LabVIEW can help save you time and frustration by eliminating some of these steps and making others markedly easier. LabVIEW is one software tool that can span all of your hardware ponents. Drivers are readily available for mon hardware devices. Each hardware driver shares a similar, familiar programming model, and examples of how to use the model install directly into LabVIEW. (2)onnect to Any Hardware With LabVIEW, you can use all of your hardware with a single development environment. Connectivity is made possible with driver software, which serves as the munication layer between LabVIEW and your hardware. LabVIEW driver software supplies seamless integration across multiple types of instruments, buses, and sensors, including data acquisition devices。 boxed instruments。 modular instruments。 motion controllers and motor drives。 machine vision and image processing hardware。 wireless sensors。 and fieldprogrammable gate arrays (FPGAs). In the rare event that a LabVIEW driver doesn?t already exist, you also can import drivers from other programming languages or use lowlevel munication to implement your own driver. (3)I Hardware With more than 50 million I/O channels sold in the last 10 years, National Instruments is a global market leader in PCbased data acquisition, with a plete family of data acquisition products for desktop, portable, industrial, and embedded applications. You can use NIDAQmx driver software to integrate more than 200 data acquisition devices in LabVIEW on a variety of major buses and form factors, including USB, PCI, PCI Express, PXI, PXI Express, wireless, and Ether. (4)ThirdParty Hardware LabVIEW does more than just connect to NI hardware. LabVIEW also connects 12 to thousands of thirdparty instruments through instrument drivers. The Instrument Driver Network (IDNet) offers more than 8,000 free drivers for instruments from more than 275 thirdparty vendors that make your hardware work with LabVIEW. From： 13 虛擬儀器 1．概述 LabVIEW 是一種程序開發(fā)環(huán)境，由美國國家儀器（ NI）公司研制開發(fā)的，類似于 C 和 BASIC 開發(fā)環(huán)境， 但是 LabVIEW 與其他計算機(jī)語言的顯著區(qū)別是：其他計算機(jī)語言都是采用基于文本的語言產(chǎn)生代碼，而 LabVIEW 使用的是圖形化編輯語言 G 編寫程序，產(chǎn)生的程序是框圖的形式。 LabVIEW 是一個完全的、開放式的虛擬儀器開發(fā)系統(tǒng)應(yīng)用軟件，利用它組建儀器測試系統(tǒng)和數(shù)據(jù)采集系統(tǒng)可以大大簡化程序的設(shè)計。 LabVIEW與 Visual C++、Visual Basic、 LabWindows/CVI 等編程語言不同，后者采用的是基于文本語言的程序代碼（ Code），而 LabVIEW 則是使用圖形化程序設(shè)計語言 G（ Graphic），用框圖代替了傳統(tǒng)的程序代碼。 LabVIEW 所運用的設(shè)備圖標(biāo)與科學(xué)家、工程師們習(xí)慣的大部分圖標(biāo)基本一致，這使得編程過程和思維過程非常的相似。 LabVIEW可方便的調(diào)用 Windows動態(tài)鏈接庫和用戶自定義的動態(tài)鏈接庫中的函數(shù)； LabVIEW 還提供了 CIN (C Interface Node) 節(jié)點使得用戶可以使用由 C或 C++語言，如 ANSI C, 編譯的程序模塊，使得 LabVIEW 成為一個開放的開發(fā)平臺。 LabVIEW 還直接支持動態(tài)數(shù)據(jù)交換 （ DDE）、結(jié)構(gòu)化查詢語言（ SQL）、 TCP和 UDP 網(wǎng)絡(luò)協(xié)議 等。此外， LabVIEW 還提供了專門用于程序開發(fā)的工具箱，使得用戶能夠很方便的設(shè)置斷點，動態(tài)的執(zhí)行程序來非常直觀形象的觀察數(shù)據(jù)的傳輸過程，以及進(jìn)行方便的調(diào)試。 LabVIEW 的運行機(jī)制就宏觀上講已經(jīng)不再是傳統(tǒng)上的馮 諾伊曼計算機(jī)體系結(jié)構(gòu)的執(zhí) 行方式了。傳統(tǒng)的計算機(jī)語言（如 C）中的順序執(zhí)行結(jié)構(gòu)在 LabVIEW中被并行機(jī)制所代替； 從本質(zhì)上講，它是一種帶有圖形控制流結(jié)構(gòu)的數(shù)據(jù)流模式（ Data Flow Mode），這種方式確保了程序中的函數(shù)節(jié)點（ Function Node）只有在獲得它的全部數(shù)據(jù)后才能夠被執(zhí)行 。 也就是說，在這種數(shù)據(jù)流程序的概念中，程序的執(zhí)行是數(shù)據(jù)驅(qū)動的，它不受操作系統(tǒng)、計 算機(jī)等因素的影響。 既然 LabVIEW 程序是數(shù)據(jù)流驅(qū)動的，數(shù)據(jù)流程序設(shè)計規(guī)定，一個目標(biāo)只有當(dāng)它的所有輸入有效時才能夠被執(zhí)行；而目標(biāo)的輸出只有當(dāng)它的功能完全時才是有效的。這樣， Lab VIEW 中被連接的函數(shù)節(jié)點之間的數(shù)據(jù)流控制著程序的執(zhí)行次序，而不像文本程序受到行順序執(zhí)行的約束。從而，我們可以通過相互連接函數(shù)節(jié)點快速簡潔的開發(fā)應(yīng)用程序，甚至還可以有多個數(shù)據(jù)通道同步運行，即所謂的多線程（ Multithreading）。 14 2． 結(jié) 合 NI LabVIEW 的數(shù)據(jù)存儲和報告 處理與存儲容量的持續(xù)增長、硬件與軟件成本的降低，造成收集的數(shù)據(jù)