Home > Articles > Programming

  • Print
  • + Share This
This chapter is from the book

Demonstration Examples

Okay, you have had enough reading for now. To get an idea of how LabVIEW works, you can open and run a few existing LabVIEW programs.

NI Example Finder

LabVIEW ships with many working examples that will help you learn common programming techniques and see applications that accomplish common hardware input/output and data processing tasks. The NI Example Finder is a very useful tool that assists in the search for these examples. You can open the NI Example Finder, shown in Figure 1.7, by launching LabVIEW and then going to the Help menu and selecting Find Examples . . . .

01lve07.jpg

Figure 1.7 The NI Example Finder

If you are just getting started with LabVIEW, you will want to set the Browse according to: option to Task and start exploring inside the Industry Applications folder. This folder contains demonstration and simulation applications, which are an excellent place to begin learning about LabVIEW. If you are looking for an example on a topic that you don't see listed in the folder tree view, you can switch to the Search tab of the Example Finder and perform a keyword search.

Examples on the CD

Whether you are using the Professional, Full, or Evaluation version of LabVIEW, just launch it. Make sure you can access the EVERYONE directory from the CD or your hard drive, as described in the Preface; it contains the activities for this book. After launching LabVIEW, a dialog box will appear. To open an example, select Open VI and choose the one you want.

Activity 1-1: Temperature System Demo

Open and run the VI called Temperature System Demo.vi by following these steps:

  1. Launch the NI Example Finder, as described in the NI Example Finder section of this chapter.

  2. With the Browse tab selected and the Browse according to: option set to Task, navigate the folder tree to "Industry Applications," then "Analysis." Double-click "Temperature System Demo.vi" to open it. This VI may also be found using the File>>Open menu option and browsing to the following location, beneath the LabVIEW installation folder:

  3. examples/apps/tempsys.llb/Temperature System Demo.vi
       
  4. You will see the VI shown in Figure 1.8.

    01lve08.jpg

    Figure 1.8 Temperature System Demo.vi front panel

  5. ICON TYPE Run Button Inactive

    ICON TYPE Run Button Active

    ICON TYPE Abort Button

    Run the VI by clicking on the Run button, located on the VI's Toolbar (the Toolbar is the row of icons beneath the VI's menubar). The Run button will change appearance to indicate that the VI is running. Other buttons on the Toolbar may also change appearance (or disappear) because certain buttons are only applicable while the VI is running (such as the Abort button), and others are only applicable while the VI is not running (such as those used for editing).

    Notice also that the Abort button becomes active in the Toolbar. You can press it to abort program execution.

    Temperature System Demo.vi simulates a temperature monitoring application. The VI makes temperature measurements and displays them in the thermometer indicator and on the chart. Although the readings are simulated in this example, you can easily modify the program to measure real values. The Update Period slide controls how fast the VI acquires the new temperature readings. LabVIEW also plots high and low temperature limits on the chart; you can change these limits using the Temperature Range knobs. If the current temperature reading is out of the set range, LEDs light up next to the thermometer.

    This VI continues to run until you click the Acquisition switch to off. You can also turn the data analysis on and off. The Statistics section shows you a running calculation of the mean and standard deviation, and the Histogram plots the frequency with which each temperature value occurs.

Tweaking Values

  1. ICON TYPE Operating Tool

    Use the cursor, which takes on the personality of the Operating tool while the VI is running, to change the values of the high and low limits. Highlight the old high or low value, either by clicking twice on the value you want to change, or by clicking and dragging across the value with the Operating tool. Then type in the new value and click on the enter button, located next to the run button on the Toolbar. Also, try changing the high and low limits using the round knob controls. Note how changing the values with the knobs takes effect instantly.

  2. ICON TYPE Enter Button

    Change the Update Period slide control by placing the Operating tool on the slider, and then clicking and dragging it to a new location.
    You can also operate slide controls using the Operating tool by clicking on a point on the slide to snap the slider to that location, by clicking on a scroll button to move the slider slowly toward the arrow, or by clicking in the slide's digital display and entering a number.

  3. Try adjusting the other controls in a similar manner.

  4. Stop the VI by clicking on the Acquisition switch.

Examine the Block Diagram

The block diagram shown in Figure 1.9 represents a complete LabVIEW application. You don't need to understand all of these block diagram elements right now—we'll deal with them later. Just get a feel for the nature of a block diagram. If you already do understand this diagram, you'll probably fly through the first part of this book!

01lve09.jpg

Figure 1.9 Temperature System Demo.vi block diagram

  1. Open the block diagram of Temperature System Demo.vi by choosing Show Diagram from the Windows menu—or you can use the <ctrl>-E shortcut on Windows, <command>-E on Mac OS X, or <meta>-E on Linux.

  2. Examine the different objects in the diagram window. Don't panic at the detail shown here! These structures are explained step by step later in this book.

  3. ICON TYPE Highlight Execution Button

    Open the contextual Help window by choosing Show Context Help from the Help menu—or you can use the <ctrl>-H shortcut on Windows, <command>-H on Mac OS X, or <meta>-H on Linux. Position the cursor over different objects in the block diagram and watch the Help window change to show descriptions of the objects. If the object is a function or subVI, the Help window will describe the inputs and outputs as well.

  4. ICON TYPE Highlight Execution Button (Active)

    Turn on execution highlighting by clicking on the Highlight Execution button, so that the light bulb changes to the active (lighted) state. With execution highlighting turned on, you can watch the data flow through the wires. You will see small data bubbles that travel along the wires, representing the data flowing through the wires. We will learn more about this and other useful debugging tools in Chapter 5.

Hierarchy

LabVIEW's power lies in the hierarchical nature of its VIs. After you create a VI, you can use it as a subVI in the block diagram of a higher-level VI, and you can have as many layers of hierarchy as you need. To demonstrate this versatile ability, look at a subVI of Temperature System Demo.vi.

  1. ICON TYPE Temperature Status subVI

    Open the Temperature Status subVI by double-clicking on its icon. The front panel shown in Figure 1.10 springs to life.

    01lve10b.jpg

    Figure 1.10 The front panel of the Temperature Status subVI

Icon and Connector

The icon and connector provide the graphical representation and parameter definitions needed if you want to use a VI as a sub-routine or function in the block diagrams of other VIs. They reside in the upper-right corner of the VI's front panel window. The icon graphically represents the VI in the block diagram of other VIs, while the connector terminals are where you must wire the inputs and outputs. These terminals are analogous to parameters of a subroutine or function. You need one terminal for each front panel control and indicator through which you want to pass data to the VI. The icon sits on top of the connector pattern until you choose to view the connector.

01lve11.jpg

Figure 1.11 Temperature Status.vi Icon and Connector Pane

By using subVIs, you can make your block diagrams modular and more manageable. This modularity makes VIs easy to maintain, understand, and debug. In addition, you can often create one sub-VI to accomplish a function required by many different VIs.

Now run the top-level VI with both its window and the Temperature Status subVI window visible. Notice how the subVI values change as the main program calls it over and over.

  1. Select Close from the File menu of the Temperature Status subVI. Do not save any changes.

  2. Select Close from the File menu of Temperature System Demo.vi, and do not save any changes.

Activity 1-2: Frequency Response Example

This example measures the frequency response of an unknown "black box." A function generator supplies a sinusoidal input to the black box (hint: it contains a bandpass filter, which lets only certain signal components through it). A digital multi-meter measures the output voltage of the black box. Although this VI uses subVIs to simulate a function generator and a digital multimeter, real instruments could easily be hooked up to a real black box to provide real-world data. You would then use sub-VIs to control data acquisition, GPIB transfers, or serial port communication to bring in or send out real data instead of simulating it.

You will open, run, and observe the VI in this activity.

  1. Launch the NI Example Finder, as described in the NI Example Finder section of this chapter.

  2. With the Browse tab selected and the Browse according to: option set to Task, navigate the folder tree to "Industry Applications," and then "Instrument Input and Output." Double-click "Frequency Response.vi" to open it. (Note: You can also find this example in the LabVIEW install directory, under examples/apps/freqresp.llb.)

  3. You will see the VI shown in Figure 1.12.

  4. 01lve12.jpg

    Figure 1.12 Frequency Response.vi front panel

  5. ICON TYPE Run Button

    Run the VI by clicking on the run button. You can specify the amplitude of the input sine wave and the number of steps the VI uses to find the frequency response by changing the Amplitude control and the Number of Steps control, and then running the VI again. You can also specify the frequency sweep by inputting the upper and lower limits with the Low Frequency and High Frequency knobs. Play with these controls and observe the effect they have on the output of the "black box."

  6. Open and examine the block diagram by choosing Show Diagram from the Window menu.

  7. Close the VI by selecting Close from the File menu. These exercises should give you a basic feel for LabVIEW's "G" programming environment. With the G language, you'll find writing powerful applications (and debugging them) to be a snap! Read on to learn how.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020