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  • Lab3: introduction to Labview

    Introduction:-

    Labview is a graphical programming language that uses items instead

    of lines of text.

    Labview uses dataflow programming but in text-based programming

    languages, instructions determine the program execution

    You can build a user interface using Labview and the user interface is

    known as Front pane

    Labview programs are called virtual instruments, because their

    appearance and operation imitate the physical instruments

    Labview program consists of two components:

    Front panel: serves as a user interface

    Block diagram: contains the graphical code source

    Front panel:

    The front panel contains the user interface which can be built by controls

    like knobs, pushbutton, LEDS and toggle switches. The front panel is used

    to simulate the input devices and supply data to the block diagram. In

    addition to that it is used to display the output of the block diagram graphical

    code. The front panel is shown in figure 1. The front panel contains the

    control palette. The control palette is found only on the front panel. The

    control palette is shown in figure 2

  • Figure 1Front panel screen

    Figure 2 Control palette

  • Block diagram panel:

    The block diagram screen contains the graphical code. The items on the

    front panel appear as terminals in the block diagram screen. The block

    diagram panel contains the functions palette which is available only on the

    block diagram screen. The block diagram and the function palette are shown

    in figure 3 and figure 4.

    Figure 3 block diagram screen

  • What Do the Different Colors of Wires in Labview Indicate?

    To construct a complete code using Labview you need to wire the blocks in

    the block diagram screen. Wires have different colors each color indicates a

    type of data

    Green Boolean data type (0,1)

    Blue Integer

    Orange Floating point (double)

    pink String data type

    Figure 4 Functions palette

  • Contents of the control palette:

    Name Use

    Num Ctrls Use to input a number

    through knobs , dials ,

    and slides

    Buttons Use to insert a

    pushbutton or toggle

    switch and slide switch

    Text Ctrls User to inter a string or

    to display a string or to

    make a label to make to

    code more realistic and

    readable

    leds Used as indicators

    Graph indicator Used to display a graph

    on the front panel

    Contents of the function palette:

    Name Use

    Input Use to create an input

    like a simulated signal

    and DAC input or voice

    input

    Output Use to create an output

    like a DAC output

    Exec control Use to create case

    structure and loops

    Arith & comp Use to make the

    arithmetic operations

    and comparison

    operations

  • Example (1):-

    Make a labview program that ask the user to enter(x,y) two numbers and the

    program find :

    X+y

    X*y

    X^y

    x-y

    x/y if y equal zero (answer equal infinity) a red led should light to

    warn the user

    solution:

    The purpose of this program is to learn the arithmetic operations like (add ,

    subtract , division , multiplication). The front panel should contain two input

    for the two number and four output for the for operation and a warning led

    as shown in figure 5

    figure 6 shows the block diagram screen

    Figure 5 front panel of example 1

  • comment :

    Note that Labview complete the division operator when the denumerator

    equals zero

    Example (2) (Formula)

    Make a labview program to execute the following formula :

    Y1=10x1 + 5

    Y2=(x1*x2)2+20x3

    Y3=sinx2+cosx3

    Solution

    Figure 6 block diagram of example 1

  • The front panel should contain three inputs and three outputs as shown in

    figure 7

    Figure 8 shows the block diagram screen:

    Figure 7 front panel of example 2

    Figure 8 block diagram of example 2

  • Comment

    Formula tool can be found at arithmetic and comparison and is used to

    enter a formula in an easy way for the user

    Example 3

    Make a labview program that takes the mark of a student. The program

    contain five leds as following :

    Led 1 Mark( 90-100)

    Led 2 Mark(80-89)

    Led 3 Mark (70-79)

    Led 4 Mark (60-69)

    Led 5 Fail

    If the formula is

    correct then this

    led is green

  • Solution :-

    The purpose for this example is to learn the comparison operators. The front

    panel should contain five led as output and one input for the mark as shown

    in figure 9

    Figure 10 shows the block diagram screen

    Figure 9front panel of example 3

  • Example 4 graph in labview

    Make a labview program that plot a sine wave and control its frequency,

    amplitude and phase

    Solution

    The program should contain three knobs (frequency, phase, amplitude) and a

    graph screen to show the output.

    Figure 11 shows the front panel of the system

  • Figure 12 shows the block diagram of example 4

    Figure 11 front panel of example 4

    Figure 12 block diagram of example 4

  • Comment :

    Simulated signal can be found on the function palette >> input

    What happen when increasing the frequency over 500?why?

    To choose

    the signal

    type

    To add noise

    to the signal

  • Example 5

    Make a Labview program that plot two signals on the same graph and

    control each signal amplitude and frequency and phase, the first signal is

    sine and the second is triangle.

    Solution

    the program should contain six knobs (two signals) and one graph screen as

    shown in figure 13

    Figure 13 front panel of example 5

  • Figure 14 shows the block diagram of example 5

    Example 6

    Make a Labview program that plots a sine signal or a square according to a

    toggle switch control by the user. If the switch is on then the plotted signal is

    sine if the switch is off then the plotted signal is square and add noise to

    each signal with the noise amplitude is control by the user

    Solution

    This example contain four knobs (frequency ,phase, amplitude, noise

    amplitude ) as shown in figure 15

    Figure 14 block diagram of example 5

    Use to plot to signal on the

    same graph similar to hold on

    instruction in Matlab and can

    be found at function palette>>

    signal manipulation

  • Figure 15 front panel of example 6

  • Figure 16 shows Block diagram of example 6

    Figure 16 block diagram of example 6

    The select operator can be found

    in arithmetic and comparison

    >>comparison

    Work as a multiplexer with a

    selector to choose the output

  • Report exercises:-

    1- Make a Labview program that calculate the average of four number if

    the average is bigger than 100 then a green led will be on and if equal

    a yellow led will be on and if less a red led will be on.

    2- Make a Labview program that execute the following formula

    1 2 20y x x

    1 2 3* *y x x x

    2

    1( )y x

    3- Make a Labview program that plot two signal (sine and saw tooth) on

    the same graph and control the amplitude and phase and frequency of

    each signal

    4- (bonus) make a Labview that select one signal out of four signal to plot and the program contain only for knobs (amplitude, phase ,

    frequency , noise amplitude) and two toggle switches and one graph

    screen