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Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI A. Virtual Instruments (VIs) The appearance and operation of VIs imitate physical instruments, such.

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Presentation on theme: "Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI A. Virtual Instruments (VIs) The appearance and operation of VIs imitate physical instruments, such."— Presentation transcript:

1 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI A. Virtual Instruments (VIs) The appearance and operation of VIs imitate physical instruments, such as oscilloscopes and digital multimeters. 1 Virtual Instrument (VI) – A LabVIEW program

2 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Parts of a VI LabVIEW VIs contain three main components: 1. Front Panel 2. Block Diagram 3. Icon/Connector Pane 2

3 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Parts of a VI – Front Panel You build the front panel with controls (inputs) and indicators (outputs) 3 Front Panel – User interface for the VI

4 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Parts of a VI – Block Diagram Front panel objects appear as terminals on the block diagram 4 Block Diagram – Contains the graphical source code

5 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Parts of a VI – Icon/Connector Pane Icon: graphical representation of a VI Connector Pane: map of the inputs and outputs of a VI Icons and connector panes are necessary to use a VI as a subVI A subVI is a VI that is inside of another VI Similar to a function in a text-based programming language IconConnector Pane 5

6 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Controls Palette Contains the controls and indicators you use to create the front panel Access from the front panel by selecting View»Controls Palette 6

7 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Controls & Indicators Controls Knobs, push buttons, dials, and other input devices Simulate instrument input devices and supply data to the block diagram of the VI Indicators Graphs, LEDs, and other displays Simulate instrument output devices and display data the block diagram acquires or generates 7

8 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Numeric Controls/Indicators The numeric data type can represent numbers of various types, such as integer or real 8 Numeric Indicator Numeric Control Increment/Decrement Buttons

9 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Boolean Controls/Indicators The Boolean data type represents data that only has two parts, such as True and False or On and Off Use Boolean controls and indicators to enter and display Boolean (True or False) values Boolean objects simulate switches, push buttons, and LEDs 9 Boolean Control Boolean Indicator

10 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Strings The string data type is a sequence of ASCII characters Use string controls to receive text from the user such as a password or user name Use string indicators to display text to the user 10

11 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Shortcut Menus All LabVIEW objects have associated shortcut menus As you create a VI, use the shortcut menu items to change the look or behavior of front panel and block diagram objects To access the shortcut menu, right-click the object 11

12 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Property Dialog Box Right-click a front panel object and select Properties to display The options available on the property dialog box are similar to the options available on the shortcut menu for that object 12

13 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI E. Front Panel – Configure Multiple Objects Select multiple objects to simultaneously configure shared properties 13

14 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Configuring Your LabVIEW Environment Functions Palette Tack the Functions palette and select Customize»Change Visible Categories then click Select All Controls Palette Tack the Controls palette and select Customize»Change Visible Categories then click Select All

15 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Pratice Replicate the following front panel

16 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram Block diagram objects include the following: Terminals SubVIs Functions Constants Structures Wires 16

17 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Terminals Terminals are: Block diagram appearance of front panel objects Entry and exit ports that exchange information between the front panel and block diagram Analogous to parameters and constants in text-based programming languages Change the view type of a terminal by toggling the View as Icon selection from the context menu 17

18 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram Terminals 18

19 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. LabVIEW Data Types – Terminals Terminals visually communicate information about the data type represented

20 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Wires Transfer data between block diagram objects through wires Wires are different colors, styles, and thicknesses, depending on their data types A broken wire appears as a dashed black line with a red X in the middle 20 Scalar 1D Array 2D Array DBL NumericInteger NumericString

21 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Nodes Objects on the block diagram that have inputs and/or outputs and perform operations when a VI runs Analogous to statements, operators, functions, and subroutines in text-based programming languages Nodes can be functions, subVIs, or structures 21 Nodes

22 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI H. Selecting A Tool Create, modify, and debug VIs using the tools provided by LabVIEW A tool is a special operating mode of the mouse cursor The operating mode of the cursor corresponds to the icon of the tool selected When using the Automatic Tool Selection, LabVIEW chooses which tool to select based on the current location of the mouse 22

23 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Practice Look and the block diagram of the previous practice and add the following nodes: Add Multiply Random number Greater than Less than Get date/time in seconds Then use wires to connect all the elements of the block diagram leaving no terminal unconnected. Target: Simulate a given temperature value, add a random noise of given amplitude, then light up an alert when such a temperature is greater than setpoint and another if is less than setpoint.

24 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Practice solution

25 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Function Nodes Fundamental operating elements of LabVIEW Do not have front panels or block diagrams, but do have connector panes Double-clicking a function only selects the function – does not open it like a VI Has a pale yellow background on its icon 25

26 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – SubVI Nodes SubVI: VIs that you build to use inside of another VI Any VI has the potential to be used as a subVI When you double-click a subVI on the block diagram, you can view the front panel and block diagram of the subVI The upper right corner of the front panel and block diagram displays the icon for the current VI This is the icon that appears when you place the VI on a block diagram as a subVI 26

27 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Wires Transfer data between block diagram objects through wires Wires are different colors, styles, and thicknesses, depending on their data types A broken wire appears as a dashed black line with a red X in the middle 27 Scalar 1D Array 2D Array DBL NumericInteger NumericString

28 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. LabVIEW Data Types – Terminals Terminals visually communicate information about the data type represented

29 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. LabVIEW Data Types – Numerics The numeric data type represents numbers of various types To change the representation of a numeric, right-click the control, indicator, or constant, and select Representation from the shortcut menu

30 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. LabVIEW Data Types – Boolean Behavior of Boolean controls is specified by the mechanical action In LabVIEW, the Boolean data type is represented with the color green

31 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Mechanical Action of Booleans Use the Mechanical Action of Booleans VI located in the NI Example Finder to learn about the different switch and latch actions.

32 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Data Types – String A sequence of displayable or non-displayable ASCII characters On the front panel, strings appear as tables, text entry boxes, and labels Change the display type from the short-cut menu: Normal, \ Codes, Password and Hex Edit and manipulate strings with the String functions on the block diagram In LabVIEW, the string data type is represented with the color pink

33 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Data Types – Enum An enum represents a pair of values, a string and a numeric, where the enum can be one of a defined list of values

34 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Data Types – Enum Enum: enumerated control, constant, or indicator Enums are useful because it is easier to manipulate numbers than strings on the block diagram

35 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI B. Data Types – Dynamic Stores the information generated or acquired by an Express VI Non-Express VIs do not accept the dynamic data type To use a built-in VI or function to analyze or process the dynamic data type, you must convert the data type Numeric, waveform, or Boolean data indicators or inputs automatically convert the dynamic data type when wired In LabVIEW, the dynamic data type is represented with the color dark blue

36 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Wiring Tips Press -B to delete all broken wires Right-click and select Clean Up Wire to reroute the wire 36

37 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI F. Block Diagram – Wiring Tips Use the Clean Up Diagram tool to reroute multiple wires and objects to improve readability 1.Select a section of your block diagram 2.Click the Clean Up Diagram button on the block diagram toolbar 37

38 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Dataflow LabVIEW follows a dataflow model for running VIs A node executes only when data are available at all of its input terminals A node supplies data to the output terminals only when the node finishes execution 38

39 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Dataflow – Quiz Which node executes first? a)Add b)Subtract c)Random Number d)Divide e)Sine 39

40 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Dataflow – Quiz Answers NO CORRECT ANSWER Which node executes first? a)Add – possibly b)Subtract – definitely not c)Random Number – possibly d)Divide – possibly e)Sine – definitely not 40

41 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI SummaryQuiz 1.Which function executes first: Add or Subtract? a)Add b)Subtract c)Unknown 41

42 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI SummaryQuiz Answer 1.Which function executes first: Add or Subtract? a)Add b)Subtract c)Unknown 42

43 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures Have two or more subdiagrams or cases Execute and displays only one case at a time An input value determines which subdiagram to execute Similar to case statements or if...then...else statements in text-based programming languages

44 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures Case Selector Label: contains the name of the current case and decrement and increment buttons on each side Selector Terminal: Wire an input value, or selector, to determine which case executes

45 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI Practice Add to the previous practice a button in order to update the string label ONLY if the button is pressed. Then run. Change its mechanical action and run again. Create a enum control with items Heating, Cooling, Conditioning and use its values to turn on label too hot only, label too cold only, or both, according to the case selected. Make the string indicator display Hi there! if the user inputs Hello, or the same input string if otherwise.

46 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Default Case You can specify a default case for the Case structure If you specified cases for 1, 2, and 3, but you get an input of 4, the Case structure executes the default case Right-click the Case structure border to add, duplicate, remove, or rearrange cases and to select a default case

47 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Input & Output Tunnels You can create multiple input and output tunnels Inputs are available to all cases if needed You must define each output tunnel for each case

48 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Use Default if Unwired Default values are: Avoid using the Use Default If Unwired option on Case structure tunnels Adds a level of complexity to your code Complicates debugging your code Data TypeDefault Value Numeric0 BooleanFALSE StringEmpty

49 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Boolean Boolean input creates two cases: True and False

50 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Integer Add a case for each integer as necessary Integers without a defined case use the default case

51 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – String Add a case for each string as necessary Strings without a defined case use the default case

52 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures – Enum Gives users a list of items from which to select The case selector displays a case for each item in the enumerated type control

53 Gruppo di Misure Meccaniche e Termiche UNIBS - DIMI I. Case Structures - Error Checking and Error Handling Use Case Structures inside VIs to execute the code if there is no error and skip the code if there is an error


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