Home > Articles

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

This chapter is from the book

1.2 Demonstration Examples

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

Whether you are using the 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.


Throughout this book, use the left mouse button (if you have more than one) unless we specifically tell you to use the right one. On MacOS computers, <command>-click when right-mouse functionality is necessary. In most LabVIEW situations, the <control> key on Windows will correspond to <command> on Macs, <meta> on Suns, and <alt> on Linus and HP machines.

1.2.1 Activity 1-1: Temperature System Demo

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

  1. Launch LabVIEW if you haven't already.

  2. Select Open from the File menu, or click the Open VI button if you have the LabVIEW start-up dialog box.

  3. Next, open the Everyone directory or folder by double-clicking on it. Then select the libary CH1.LLB (Note: A library in LabVIEW, noted with the .llb extension, is a virtual directory of VI files. You can only see what's inside a library from LabVIEW—to the operating system, it looks like a single file). Finally, open Temperature System Demo.vi. (If you have the full version of LabVIEW, you can also find this example under examples/apps/tempsys.llb). After a few moments, the Temperature System Demo front panel window appears, as shown in Figure 1.7. The front panel contains numeric controls, Boolean switches, slide controls, knob controls, charts, graphs, and a thermometer indicator.

    Figure 1.7Figure 1.7 Temperature System Demo test front panel window.

  4. buttons
  5. Run the VI by clicking on the Run button. The button changes appearance to indicate that the VI is running. The Toolbar, which is the row of icons on the top bar of the screen, also changes, since editing functionality won't be necessary while the VI is running.

    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. 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.

  2. buttonsChange 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.


Even though the display changes, LabVIEW does not accept the new values in digital displays until you press the enter button, or click the mouse in an open area of the window.

  • Try adjusting the other controls in a similar manner.

  • Stop the VI by clicking on the Acquisition switch.

  • Examine the Block Diagram

    The block diagram shown in Figure 1.8 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!

    Figure 1.8Figure 1.8

    1. Open the block diagram of Temperature System Demo.vi by choosing Show Diagram from the Windows menu.

    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. Open the contextual Help window by choosing Show Context Help from the Help menu. 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.


    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. Open the Temperature Status subVI by double-clicking on its icon.


      The front panel shown in Figure 1.9 springs to life.

      Figure 1.9Figure 1.9

    Icon and Connector

    The icon and connector provide the graphical representation and parameter definitions needed if you want to use a VI as a subroutine 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.

    Figure 1.10Figure 1.10

    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 subVI 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.


      Selecting Close from the File menu of a VI diagram closes the block diagram window only. Selecting Close on a front panel window closes both the panel and the diagram.

    1.2.2 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 multimeter 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 subVIs 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. Select Open from the File menu to open the VI, or click the Open VI button if you have the LabVIEW dialog box.

    2. Select the EVERYONE directory and then CH1.LLB. Finally, double-click on Frequency Response.vi. (If you have the full version of LabVIEW, you can also find this example under examples/apps/_freqresp.llb.) The front panel shown in Figure 1.11 should appear.

      Figure 1.11Figure 1.11

    3. 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 run 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."

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

    5. Close the VI by selecting Close from the File menu. These exercises should give you a basic feel for LabVIEW's programming environment. With LabVIEW, 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.


    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.


    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.


    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.


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


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


    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.


    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.


    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