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