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LabVIEW1．overviewLabVIEW is a program development environment, by the national instruments (NI) research and development company, similar to the C and BASIC development environment, but with other computer language LabVIEW significant difference is: other computer language is based on the text, and the language code of graphical LabVIEW use scripting language G program, application is in the form of block diagram.A complete, LabVIEW virtual instrument system of open application software development, and use it to form instrument testing system and data collecting system can simplify the design procedure. With Visual C++ LabVIEW, Visual Basic,LabWindows/CVI, etc, which adopts different programming language is based on the text language program Code (Code), and abVIEW L is using graphical programming language), Graphic (G instead of the traditional diagram of the Code. The Lab VIEW of equipment with the scientists and engineers icon in the habit of basic agreement, this makes the icon programming process and thinking process is very similar.LabVIEW convenient calls Windows DLL and user-defined function in the DLL, LabVIEW also provides CIN (C) Node with any users can use by C + + language or, if the ANSI C, compiled program modules, makes a open LabVIEW development platform. LabVIEW also directly support dynamic data exchange (DDE), structured query language (SQL), TCP and UDP network protocol. In addition, the LabVIEW also provides special used for program development kit, users can easily set breakpoints, dynamic program execution to very intuitive image observation data transmission process, and convenient debug.The operation mechanism is LabVIEW macroeconomic sense is no longer the von neumann traditionally computer system structure of the method. The traditional computer language (such as C) to the order of execution by parallel structure in LabVIEW mechanism; Essentially, it is a kind of control Flow structure with graphical Data Flow pattern (Data Flow Mode), this kind of means to ensure the process of any Node Function in hire those knowledgeable programmers only after all it can only be executed Data.That is to say, in the data flow in the concept of program execution, and it is the data driven by operating system, calculate machine and so on.Since LabVIEW program is data flow driven, data flow design program, a goal only when it's all input can only be effective, And the goal of output only when it is complete. So, in VIEW of the Lab is connected the data flow between nodes function control program execution sequence, and don't like text program execution sequence by rows of constraint. Thus, we can be connected through the rapid development of concise function node applications, even can have multiple data synchronization operation channel, the so-called Multithreading (Multithreading).2．Data Storage and Reporting with NI LabVIEWThe continued increase in processing and storage capacity and the decrease of hardware and software costs has resulted in an explosion of collected data being acquired. But while technology is enabling faster and richer data retention, storing, managing, and sharing data remains the real challenge. Traditional software packages tend to take one of two limiting approaches: 1) they force you into a particular format that is not exchangeable with other applications or users or 2) saving data is left so open ended you waste time trying to determine the best way to organize and save your data to disk so you can share it.NI LabVIEW, designed for the entire engineering process, includes built-in functionality to help you easily save data to disk and create professional reports. By providing easy yet robust interfaces for file I/O and reporting, you can make the most of your acquired data to make decisions faster.(1)File I/O Designed Specifically for Engineering DataDespite the fact that LabVIEW offers a wide variety of file I/O options, these traditional file types rarely meet all the criteria you need in a file format. For example, ASCII files are exchangeable, but are very large and slow to read and write. On the other hand, binary file read and write speeds can keep up with high-speed hardware, but are difficult to share with others.Because of the drawbacks of traditional file I/O, National Instruments developed the Technical Data Management Streaming (TDMS) file format to meet the specific needs and high demands of engineers and scientists. TDMS files are based on the TDM data model for saving well-organized and documented test and measurement data. The TDM data model offers three levels of hierarchy, as shown in Figure 2 – file, group, and channel. The file level can contain an unlimited number of groups, and each group can contain and unlimited number of channels. Because of this channel grouping, you can organize your data to make it easier to understand. For example,you may have one group for your raw data and another group for your analyzed data within one file, or you may have multiple groups that correspond to sensor types or locations.Figure 1. The TDM data model meets the specific requirements of measurementdata.Also, you can insert your own custom properties at each of the three levels. Each level accepts an unlimited number of custom-defined attributes to achieve well-documented and search-ready data files. The descriptive information located in the TDMS file, a key benefit of this model, provides an easy way to document the data much like you would document code. As your documentation requirements increase, you do not have to redesign your application, you simply extend the data model to meet your needs.(2)Multiple Easy-to-Use Programming InterfacesBecause it was developed to meet the needs of all engineers, TDMS offers ease of use, high-speed streaming, and exchangeability. Like many operations in LabVIEW, you can use multiple interfaces to write TDMS files. Y ou can quickly read and write TDMS files using a virtual instrument (VI) such as the Write To Measurement File Express VI or, for the best performance and customization, use the primitive TDMS VIs from the File I/O palette. Also, when using LabVIEW with NI-DAQmx, you can use the Configure Logging VI from the DAQ palette or log directly from the NI DAQ Assistant(3)Files Exchangeable with Other Programs such as Microsoft ExcelBecause you may be required to work in additional applications, TDMS is easily exchangeable across other programs. Y ou can open TDMS files in Microsoft Excel using the TDM Excel Add-In, which installs with NI software and is available free at. Y ou also can use a C DLL for reading and writing TDMS files in other programming languages. NI is committed to helping you write well-organized and documented data using the TDMS file format, regardless of which products you use.(4)Custom and Legacy File Format Reading and WritingAlthough ideally you can choose the file format for each application you work on, you may still be restricted to reading and writing in a custom format due to legacy files or hardware that uses custom formats. Understanding that many engineers face this challenge, NI developed the DataPlugin technology so that you can use these custom formats in LabVIEW. As seen in Figure 4, a DataPlugin acts as a file parser that tells LabVIEW and other NI software how to read your custom file formats and maps them to the TDM hierarchy model in memory.Figure 2. Using a DataPlugin, you can map any file format onto the TDM datamodel.National Instruments provides more than 200 free, downloadable DataPlugins for the most common file formats. For custom formats, you can create your own DataPlugins in LabVIEW and NI DIAdem software using a documented API, or request that an NI expert create a DataPlugin for you. Using DataPlugins, you are no longer limited by custom formats and applications, and have options for how to use your data.3．Organizing and Managing Y our Data with DataFinder T echnology With many applications, the amount of data being collected can quickly become overwhelming. Typically, at that point, you might turn to a database to begin storing your data for faster search and trending. National Instruments makes it easy to interact with a database using the LabVIEW Database Connectivity Toolkit by abstracting the low-level structured query language (SQL) queries. However, moving your existing data to a database, maintaining the database, and creating applications for accessingdata can become extremely costly and time-consuming.In response to this challenge, NI developed NI DataFinder technology, included in the LabVIEW DataFinder Toolkit and DIAdem, for managing test files without the headache and expense of setting up and maintaining a large database. With NI DataFinder, you can perform Internet-like searches across all your data files, regardless of format and location within your company intranet. Simply point NI DataFinder to the location of your data files, and within seconds you can search for your files just as you would search for information on the Internet.NI DataFinder automatically builds and maintains an index of all files that meet the file type and location criteria in the NI DataFinder configuration. Y ou can use properties automatically stored in the NI DataFinder index in query conditions. When a valid data file is created, deleted, or edited, NI DataFinder automatically notices and reindexes the hierarchy and properties of the file. When you save properties not yet in NI DataFinder in a newly created file, these properties are automatically added to the index. NI DataFinder dynamically manages its own data tables and updates them based on file events and the contents of each file. Therefore, unlike many expensive database solutions, you can change and add information as your needs change without redesigning your data management solution. Using the NI DataFinder, you can quickly find trends and correlations in the large amounts of data you have saved during your tests.4.Multiple Programming Approaches in NI LabVIEWNI LabVIEW is a graphical dataflow programming environment. When using dataflow in LabVIEW, you define an execution flow in code by creating diagrams that show how data moves between functions (known as virtual instruments, or VIs). However, with LabVIEW, you can combine multiple programming approaches besides graphical data flow (G) in a single application. Use this flexibility to select your tool of choice for creating algorithms and solving an infinite variety of engineering problems.(1)Defining Programming ApproachesThe phrase …programming approaches‟ encompasses different languages for programming, models of computation, levels of abstraction, methods for interacting with existing code, and ways for representing algorithms. Over the years, National Instruments has added interfaces and methods for communication in LabVIEW to extend the number of approaches that are available.Y ou can write and import multipleapproaches into the same block diagram as the familiar G dataflow language. LabVIEW compiles all of these approaches for the appropriate hardware target, which can span desktop computers, real-time OSs, field-programmable gate arrays (FPGAs), mobile devices, and embedded processors such as ARM.1(2)Programming in GData flow, the fundamental LabVIEW programming method, was the original, and only, programming approach when NI introduced LabVIEW 1.0 in 1986. Unlike sequential-style programming, the flow of data in a dataflow program dictates when, and in what order, operations are executed. In sequential languages such as C and C++, the order of the commands in the source code (as opposed to the availability of data) determines the order in which execution will occur.G follows a dataflow model for running functions and primitives, or VIs. A block diagram function or node executes when all its inputs are available. When a node completes execution, it supplies data to its output terminals and passes the output data to the next node in the dataflow path.Figure 3. A and B are added, and the result is multiplied by C and displayed.The graphical code in Figure 2 shows how a mathematical equation can be represented in G. This diagram consists of two nodes (an add node and a multiply node), and has three numerical inputs (A, B, and C). First, A and B are added. The multiplication node does not execute until both inputs are provided, so it depends on the addition node to complete and provide the result of A + B, at which point it computes the result – (A+B)*C.Although it is possible to explicitly define variables in G, one of the most obvious differences between G code and other languages is that the functional equivalent of a traditional variable is a wire. Instead of passing variables between functions, wires define the functions to which a value is passed. Other familiar programming concepts such as While Loops, For Loops, conditional code, callback functions, and digital logic are all part of the G dataflow programming language(3)Using Configuration-Based ProgrammingIn 2003, National Instruments released NI LabVIEW 7 Express, which featured Express VIs – a new technology designed to further simplify common programming tasks and algorithm creation. Unlike traditional VIs, Express VIs abstracted tasks by offering a configuration-based approach to programming.LabVIEW distinguishes Express VIs with large blue icons. When you place an Express VI on the block diagram, a dialog appears so you can configure how the function executes. After completing the configuration, the LabVIEW development environment writes the necessary code (represented by the Express VI) for you. Y ou can view and modify this code, and you can change the Express VI configuration by simply double-clicking the Express VI icon.Consider the task of reading real-world signals into software for analysis. LabVIEW is designed to make integration with hardware for I/O simple and easy thanks to native drivers and support for thousands of instruments. However, even a task that would otherwise take a handful of VIs to execute can be simplified to a single Express VI. The DAQ Assistance Express VI prompts you to select the channels you want to send and receive I/O to and from, and configure parameters such as sample rate, terminal configuration, scales, triggering, and synchronization. Y ou also can preview the data within the interface before saving the configuration.Express VIs do not offer the same low-level control as VIs, which is why you may prefer to write the code entirely using VIs. New users interested in learning low-level constructs can easily convert an Express VI to the underlying G code by right-clicking the Express VI and selecting Open Front Panel. Normal VIs can do everything an Express VI can do. The LabVIEW Professional Development System also includes a utility for creating custom Express VIs.(4)Incorporating C-Based SyntaxWe can incorporate sequentially executed text-based syntax into a VI block diagram using one of several techniques. The Formula Node offers an inline structure that supports a syntax similar to traditional C programming. Much like C, every line ends with a semicolon and variables must have a defined scope.The Inline C Node is similar to the Formula Node with additional support and functionality for low-level programming and header files without the overhead of a function call. Y ou can use the Inline C Node for any C code, including assembly directives and #defines, that syntactically is between the curly braces in a C file.The Inline C Node is available only for targets that use generated C code. The Inline C Node is not supported for desktop Windows targets.(5)Interfacing with Built AssembliesInstead of importing source code to a LabVIEW block diagram, you may want to call into built assemblies or reuse built LabVIEW applications in other environments. Applications written in LabVIEW can easily reuse existing code and algorithms developed in other languages or programming approaches. Additionally, you might need to build an assembly from LabVIEW code, which includes the programming approaches discussed above, to be called by a different environment.LabVIEW offers multiple solutions for both scenarios. LabVIEW can call external code in DLLs or shared libraries and code exposed through ActiveX or .NET interfaces. In addition, you can reuse LabVIEW code in other programming languages by building a LabVIEW DLL or shared library, or by using ActiveX.If you have existing C code and need to reuse it in LabVIEW, one technique is to build the code as a DLL and call it using the Call Library Function Node. In fact, based on your C application architecture, you can use simple LabVIEW parallel programming to run two or more existing C routines in parallel without the additional complexity of C-based multithreaded programming. To make importing external libraries simple, LabVIEW includes the Import Shared Library Wizard, which automatically creates or updates a LabVIEW wrapper VI project library for Windows .dll file, Mac OS .framework file, or Linux .so file functions.Interfacing with the command-line is also possible with the System Exec.vi, which provides OS-specific interfaces for calling executables and other build libraries.(6)aking Advantage of Flexible ProgrammingThe combination of multiple programming approaches in a single development environment offers the advantage of reusing existing code and algorithms developed in other languages. It also makes it possible to combine simple, high-level abstractions with lower-level code that gives you more visibility and control of your application. These abstraction layers represent highly complex operations in simple, easy-to-read representations, but can be coupled with functions that give low-level control over application behavior and hardware interfaces. Thanks to tight integration with I/O, you can combine these approaches with real-world signals to take advantage of the most recent hardware technology such as multicore CPUs, FPGAs, andembedded processors.5．The Benefits of Programming Graphically in NI LabVIEW Graphical program design and programming simple, intuitive, and development of high efficiency. With the continuous development of the virtual instrument technology and graphical programming language test and control will become the most promising field development direction.Graphical programming language, which is also known as "G" language. Use this kind of language programming, basically don't write code, instead of chart or diagram. It was possible use technical personnel, scientists, engineers, familiar terminology and concepts, therefore, ICONS, LabVIEW is a tool for end users. It can enhance your own science and engineering construction, provides realizing instrument programming and convenient way of data acquisition system. Use it to research, design, testing principle and realization instrument system, can greatly improve the work efficiency.(1)abVIEW: Graphical, Dataflow ProgrammingLabVIEW is different from most other general-purpose programming languages in two major ways. First, G programming is performed by wiring together graphical icons on a diagram, which is then compiled directly to machine code so the computer processors can execute it. While represented graphically instead of with text, G contains the same programming concepts found in most traditional languages. For example, G includes all the standard constructs, such as data types, loops, event handling, variables, recursion, and object-oriented programming.The second main differentiator is that G code developed with LabVIEW executes according to the rules of data flow instead of the more traditional procedural approach (in other words, a sequential series of commands to be carried out) found in most text-based programming languages like C and C++. Dataflow languages like G (as well as Agilent VEE, Microsoft Visual Programming Language, and Apple Quartz Composer) promote data as the main concept behind any program. Dataflow execution is data-driven, or data-dependent. The flow of data between nodes in the program, not sequential lines of text, determines the execution order.This distinction may seem minor at first, but the impact is extraordinary because it renders the data paths between parts of the program to be the developer‟s main focus. Nodes in a LabVIEW program (in other words, functions, structures such as loops, subroutines, and so on) have inputs, process data, and produce outputs. Onceall of a given node‟s inputs contain valid data, that node executes its logic, produc es output data, and passes that data to the next node in the dataflow path. A node that receives data from another node can execute only after the other node completes execution.(2)ntuitive Graphical ProgrammingLike most people, engineers and scientists learn by seeing and processing images without any need for conscious contemplation. Many engineers and scientists can also be characterized as “visual thinkers,” meaning that they are especially adept at using visual processing to organize information. In other words, they think best in pictures. This is often reinforced in colleges and universities, where students are encouraged to model solutions to problems as process diagrams. However, most general-purpose programming languages require you to spend significant time learning the specific text-based syntax associated with that language and then map the structure of the language to the problem being solved. Graphical programming with G provides a more intuitive experience.Figure 4. Data originates in the acquisition function and then flows intuitively to the analysis and storage functions through wires.(3)utomatic Parallelism and PerformanceDataflow languages like LabVIEW allow for automatic parallelization. In contrast to sequential languages like C and C++, graphical programs inherently contain information about which parts of the code should execute in parallel. For example, a common G design pattern is the Producer/Consumer Design Pattern, in which two separate While Loops execute independently: the first loop is responsible for producing data and the second loop processes data. Despite executing in parallel (possibly at different rates), data is passed between the two loops using queues, which are standard data structures in general-purpose programming languages.Parallelism is important in computer programs because it can unlockperformance gains relative to purely sequential programs due to recent changes in computer processor designs. For more than 40 years, computer chip manufacturers increased processor clock speed to increase chip performance. Today, however, increasing clock speeds for performance gains is no longer viable because of power consumption and heat dissipation constraints. As a result, chip vendors have instead moved to new chip architectures with multiple processor cores on a single chip.To take advantage of the performance available in multicore processors, you must be able to use multithreading within your applications (in other words, break up applications into discrete sections that can be executed independently). If you use traditional text-based 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 built-in compiler 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 compiler tries to execute the code in parallel within a set of threads that LabVIEW manages automatically. In computer 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 field-programmable 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 IntegrationMost measurement and control hardware comes 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.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 time-wasting steps and possible incompatibilities, 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 communicate 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 components. Drivers are readily available for common 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 HardwareWith LabVIEW, you can use all of your hardware with a single development environment. Connectivity is made possible with driver software, which serves as the communication 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 field-programmable 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 low-level communication to implement your own driver.(3)I HardwareWith more than 50 million I/O channels sold in the last 10 years, National Instruments is a global market leader in PC-based data acquisition, with a complete family of data acquisition products for desktop, portable, industrial, and embedded applications. Y ou can use NI-DAQmx 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 Ethernet.(4)Third-Party HardwareLabVIEW does more than just connect to NI hardware. LabVIEW also connectsto thousands of third-party instruments through instrument drivers. The Instrument Driver Network (IDNet) offers more than 8,000 free drivers for instruments from more than 275 third-party vendors that make your hardware work with LabVIEW.From：。