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قديم 09-06-2008, 11:41 PM
الصورة الرمزية eng_a_sayed
eng_a_sayed eng_a_sayed غير متواجد حالياً
شكر وتقدير
مشــرف ســابق
 
تاريخ التسجيل: Sep 2006
المشاركات: 900
افتراضي LabView " متجدد"





تحية طيبة الى كل رواد هذا الصرح التعليمى الكبير .. الى كل متعلم ومعلم .. أما بعد
أخوانى الكرام .. أقدم لكم موضوع بعنوان LabView وسلسلة الموضوعات الخاصة به



وسيكون الوضوع خاص بتجميع جميع الموضوعات الخاصة بالبرنامج حتى يسهل الوصول الى موضوعات البرنامج بسهولة فى المنتدى ..
مع خالص الشكر والتقدير للأخ والمشرف الفاضل طارق الذى ساهم بشكل كبير فى أعداد هذا الموضوع والى كل من شارك معى فيه



وفى البداية : مقدمة عن البرنامج

أن البرمجة المعتادة بلغات البرمجة التى أعتدنا عليها والتى كانت تعتمد على كتابة البرنامج فى أكواد بخلاف الواجهة الرسومية للبرنامج ألا أنها فى أساسها أكواد تكتب ويتم تنفيد كل أمر عند الوصول اليه فى البرنامج لذا كانت تسمى control flow programming و مثل تلك العملية تستغرق الوقت الكثير، و تشتت ذهن الباحث بأمور جانبية لا علاقة لها ببحثه أو تجربته، فقامت مجموعة من الأشخاص قبل حوالي 22 سنة من الآن ، بتفكير بطرقة لحل مثل هذه المعضلة ، وبعد الكثير من الجهد و العناء توصلوا إلى فكرة بناء لغة جديدة خاصة لمثل هذه الأغراض ، و استوحوا هذه الفكرة ، من اللغة الرسمية للمهندسين ألا وهي الرسم ، بالرسم يستطيع كل المهندسين فهم ما تقول بوضوح دقيق ، و كانت مهمتهم هو تطويع هذه اللغة بحيث يفهمها الحاسوب كذلك ، و بعد ثلاث سنوات من الجهد قام تلك المجموعة المكونة من 12 شخصا بإطلاق برنامجها الجديد المبتكر لاب فيو LabVIEW ، وبهذا البرنامج تستطيع أن تبني برنامجك بمجرد وضع بعض الأيقونات و توصيلها بخط ، سلك بلغة المهندسين ، فيصبح الحاسوب قادر على تواصل مع تلك المجسات و تحليل معطياتها و حفظها ، فبدل أن تهدر يوما كاملا في كتاب ذاك البرنامج تستطيع كتابته بلاب فيو في خمس دقائق !!
بالفعل إنها ثورة في عالم الحوسبة ، و حتى تتجلى الصورة أكثر فبدلا أن تشترى معدات المتخصصة - لتحليل مخرجات المجسات- الباهظة الثمن ، يمكنك استعمال الحاسوب بدلا من ذلك بكلفة زهيدة ، فخذ مثالا ذاك الجاهز الذي يستقبل الإشارة الإلكترونية فيحفظها و يعرضها لك بالبطيء فهو يكلف 7000 ريال مثلاً, ولكن باستخدام اللاب فيو يمكنك تقليل الكلفة إلى ما يقرب 3000 ريال مع ميزة تحيل تلك الإشارة على ما تريد !!
و يوجد الآن 24000 شركة تستخدم هذا البرنامج الثوري ، و هناك العديد من الجامعات و مختبرات الأبحاث التي لا تستغني عن مثل هذا البرنامج الحيوي .
البرنامج الآن في إصدارته الثامنة، و أتمنى من جميع الجامعات أن تستخدمه في إجراء التجارب ، فهو وسيلة جيدة لحفظ الأموال و استغلال قدرات الحاسوب الضخمة ...



وسيهتم الموضوع بالتالى













بالطبع أتمنى مشاركات الجميع فى هذا الموضوع الذى اتمنى أن يأخذ حيذ كبير من حياتنا البرمجية فى الوقت المقبل

وقبل أن أنسى أليكم هذه نبذه أخرى عن البرنامج



LabVIEW (short for Laboratory Virtual Instrumentation Engineering Workbench) is a platform and development environment for a visual programming language from National Instruments. The graphical language is named "G". Originally released for the Apple Macintosh in 1986, LabVIEW is commonly used for data acquisition, instrument control, and industrial automation on a variety of platforms including Microsoft Windows, various flavors of UNIX, Linux, and Mac OS. The latest version of LabVIEW is version 8.5.1, released in April of 2008.

Dataflow programming
The programming language used in LabVIEW, called G, is a dataflow programming language. Execution is determined by the structure of a graphical block diagram (the LV-source ) on which the programmer connects different function-nodes by drawing wires. These wires propagate variables and any node can execute as soon as all its input data become available. Since this might be the case for multiple nodes simultaneously, G is inherently capable of parallel execution. Multi-processing and multi-threading hardware is automatically exploited by the built-in scheduler, which multiplexes multiple OS threads over the nodes ready for execution.
Programmers with a background in conventional programming often show a certain reluctance to adopt the LabVIEW dataflow scheme, claiming that LabVIEW is prone to race conditions. In reality, this stems from a misunderstanding of the data-flow paradigm.[citation needed] The aforementioned data-flow (which can be forced, typically by linking inputs and outputs of nodes) completely defines the execution sequence, and that can be fully controlled by the programmer. Thus, the execution sequence of the LabVIEW graphical syntax is as well-defined as with any textually language such as C, Visual BASIC, Python etc.[citation needed] Furthermore, LabVIEW does not require type definition of the variables; the wire type is defined by the data-supplying node. LabVIEW supports polymorphism in that wires automatically adjust to various types of data.

Graphical programming
LabVIEW ties the creation of user interfaces (called front panels) into the development cycle. LabVIEW programs/subroutines are called virtual instruments (VIs). Each VI has three components: a block diagram, a front panel, and a connector pane. The last is used to represent the VI in the block diagrams of other, calling VIs. Controls and indicators on the front panel allow an operator to input data into or extract data from a running virtual instrument. However, the front panel can also serve as a programmatic interface. Thus a virtual instrument can either be run as a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the given node through the connector pane. This implies each VI can be easily tested before being embedded as a subroutine into a larger program.

The graphical approach also allows non-programmers to build programs simply by dragging and dropping virtual representations of lab equipment with which they are already familiar. The LabVIEW programming environment, with the included examples and the documentation, makes it simple to create small applications. This is a benefit on one side, but there is also a certain danger of underestimating the expertise needed for good quality "G" programming. For complex algorithms or large-scale it is important that the programmer possesses an extensive knowledge of the special LabVIEW syntax and the topology of its memory management. The most advanced LabVIEW development systems offer the possibility of building stand-alone applications. Furthermore, it is possible to create distributed applications, which communicate by a client/server scheme, and are therefore easier to implement due to the inherently parallel nature of G-.

To maintain clean and legible VI user interfaces keep these tips in mind: keep panels simple and clean, maintain a consistent style, clean up wires where ever possible, and use proper terminology when labeling controls and indicators.

Benefits
One benefit of LabVIEW over other development environments is the extensive support for accessing instrumentation hardware. Drivers and abstraction layers for many different types of instruments and buses are included or are available for inclusion. These present themselves as graphical nodes. The abstraction layers offer standard software interfaces to communicate with hardware devices. The provided driver interfaces save program development time. The sales pitch of National Instruments is, therefore, that even people with limited coding experience can write programs and deploy test solutions in a reduced time frame when compared to more conventional or competing systems. A new hardware driver topology (DAQmxBase), which consists mainly of G- components with only a few register calls through NI Measurement Hardware DDK (Driver Development Kit) functions, provides platform independent hardware access to numerous data acquisition and instrumentation devices. The DAQmxBase driver is available for LabVIEW on Windows, Mac OS X and Linux platforms.

In terms of performance, LabVIEW includes a compiler that produces native for the CPU platform. The graphical is translated into executable machine by interpreting the syntax and by compilation. The LabVIEW syntax is strictly enforced during the editing process and compiled into the executable machine when requested to run or upon saving. In the latter case, the executable and the source are merged into a single file. The executable runs with the help of the LabVIEW run-time engine, which contains some precompiled to perform common tasks that are defined by the G language. The run-time engine reduces compile time and also provides a consistent interface to various operating systems, graphic systems, hardware components, etc. The run-time environment makes the portable across platforms. Generally, LV can be slower than equivalent compiled C , although the differences often lie more with program optimization than inherent execution speed.

Many libraries with a large number of functions for data acquisition, signal generation, mathematics, statistics, signal conditioning, analysis, etc., along with numerous graphical interface elements are provided in several LabVIEW package options. The number of advanced mathematic blocks for functions such as integration, filters, and other specialized capabilities usually associated with data capture from hardware sensors is immense. In addition, LabVIEW includes a text-based programming component called MathScript with additional functionality for signal processing, analysis and mathematics. MathScript can be integrated with graphical programming using "script nodes" and uses .m file script syntax that is generally compatible with Matlab.

he fully object-oriented character of LabVIEW allows reuse without modifications: as long as the data types of input and output are consistent, two sub VIs are interchangeable.

The LabVIEW Professional Development System allows creating stand-alone executables and the resultant executable can be distributed an unlimited number of times. The run-time engine and its libraries can be provided freely along with the executable.

A benefit of the LabVIEW environment is the platform independent nature of the G , which is (with the exception of a few platform-specific functions) portable between the different LabVIEW systems for different operating systems (Windows, Mac OS X and Linux). National Instruments is increasingly focusing on the capability of deploying LabVIEW onto an increasing number of targets including devices like Phar Lap OS based LabVIEW real-time controllers, PocketPCs, PDAs, FieldPoint modules and into FPGAs on special boards.

There is a low cost LabVIEW Student Edition aimed at educational institutions for learning purposes. There is also an active community of LabVIEW users who communicate through several e-mail groups and Internet forums.

Criticism
LabVIEW is a proprietary product of National Instruments. Unlike common programming languages such as C or FORTRAN, LabVIEW is not managed or specified by a third party standards committee such as ANSI.

In addition, as of version 8, all LabVIEW installs require customers to contact National Instruments by Internet or phone to "activate" the product. The increasing dependence on the vendor suggests a possible threat to privacy and data security. For example, although National Instruments claims the process is "secure and anonymous" the immediate implication is that a legal but privately installed instance of LabVIEW seems no longer possible.

Building a stand-alone application with LabVIEW requires the Application Builder component which is included with the Professional Development System but requires a separate purchase if using the Base Package or Full Development System. Compiled executables produced by the Application Builder are not truly standalone in that they also require that the LabVIEW run-time engine be installed on any target computer on which users run the application. The use of standard controls requires a runtime library for any language and all major operating system suppliers supply the required libraries for common languages such as 'C'. However, the runtime required for LabVIEW is not supplied with any operating system and is required to be specifically installed by the administrator or user. This requirement can cause problems if an application is distributed to a user who may be prepared to run the application but does not have the inclination or permission to install additional files on the host system prior to running the executable.

There is some debate as to whether LabVIEW is really a general purpose programming language (or in some cases whether it is really a programming language at all) as opposed to an application-specific development environment for measurement and automation. Critics point to a lack of features, common in most other programming languages, such as native recursion and, until version 8.20, object oriented features.

LabVIEW is also relatively expensive compared to other development suites[dubious – discuss]. LabVIEW starts at $1199 (2008 pricing) for the base version and runs up to $4499 for the NI Developer Suite. The professional edition, which is the cheapest package that bundles the application builder, costs $4099.[5] This compares to Visual Studio which starts at $299 (2008 pricing) for the standard edition and ranges up to $799 for the professional edition. LabVIEW is also available in a full featured student edition version which includes a text book for $100.

Related software
National Instruments also offers a product called Measurement Studio, which offers many of the test, measurement and control capabilities of LabVIEW, as a set of classes for use with Microsoft Visual Studio. This allows developers to harness some of LabVIEW's strengths within the text-based .NET framework.

National Instruments also offers LabWindows/CVI as an alternative for ANSI C programmers.


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مطولب كتاب Certified LabVIEW Associate Developer TeT_TaT منتدى الكتب والمجلات الالكترونية 2 18-10-2007 01:05 PM
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