LabVIEW Structures | Execution structures in Labview

Structures in LabVIEW

The structures in LabVIEW contain sections of graphical code. They control and determine when and how the code should be run in a virtual instrument (VI). A structure can be referred to as a graphical representation of a loop. It helps in iterating a piece of code as many times as we want.

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How to access structures in LabVIEW?

Open LabVIEW, and open the Front Panel. Click on the ‘View’ option from the top menu and select ‘Functions’. Choose the ‘Programming’ option and click on the ‘Structures’ icon. You will get a list of all the structures of LabVIEW. To use a structure, drag and drop them on to the block diagram.

Types of structures in LabVIEW

LabVIEW offers different kinds of structures that serve different purposes. Here is the list of structures that are available in LabVIEW.

While Loop structure
For Loop structure
Sequence structure
Flat sequence structure
Stacked sequence structure
Event structure
Timed structure
Diagram disable structure
Conditional disable structure

Let’s discuss in detail each of these structures and how to implement them.

While Loop structure

The While loop structure continues to execute a programme until a stop condition is met. When a STOP button is clicked, the while loop structure is used to keep the application continuing. Until the created value equals 50 or the STOP condition is met, and the while loop structure continues to execute and generate new values.

While loop is created as follows:

Now Create a random number generator.

As shown below, Create a multiply sign.

Now Create a constant 100.

As shown below, Create a “round of to -infinity”

As shown below, Create a “Equal to”

As before, create the constant 50.
Create an indication for the “round of to – infinity” output as

As shown below, now Wire the blocks

Once the random number generator creates the value 50, run the application to view the results. Now the while loop should stop generating new values.

You can view values being produced on LABVIEW’s “front panel” by using the “wait timer” that has been involved. This value is measured in milliseconds. There are 200 milliseconds here. There is a 200 seconds delay added between loop iterations.

For Loop structure

Using a for loop structure, the programme is repeated a specified number of times. N is the count terminal in the For loop, and “i” is the iteration terminal. Each time the loop runs, the value of “i” shifts from 0 to N-1.

Just as we did with the while loop, create the for loop.
Create a constant using input of N.
Make an indicator of i’s output.
A “wait” timer should be created as in a while loop.

Use LabVIEW to run the program. On LabVIEW’s front panel, you can see that the “current value” keeps rising. Till it reaches N-1, although this is 14 in this example.
The following is another way to store the values of “i” in an array.
Outside of the for loop, a create indicator for the output of “i.”

Execute the LabVIEW program. As soon as the program ends, all the values will be displayed in an array on LabVIEW’s front panel.

Graphs may also be created using arrays. Draw a block diagram similar to the below one. By navigating to the search bar and typing the names of the blocks that are shown on top of the blocks, such as “pi,” you may determine all the blocks.

Execute the LabVIEW program and look at the graph displayed on Labview front panel.

A For loop might not execute sometimes in a VI when the condition is not met. We can change a While loop to a For loop. To do so, right-click on the border of the While loop and select the ‘Replace with For Loop’ option from the shortcut menu.

Sequence structure

A sequence structure is utilized whenever we need a program to run in a sequential manner. The order of execution is not always under your control in LabVIEW. When a subsequent computation depends on a prior one, we are confident that it will happen in the proper sequence. However, we will not be able to control the sequence of calculations when they are being done in parallel. Calculations are compelled to occur in a predetermined sequence using a sequence structure.

Execute the program and you would see the result as below.

The two random numbers are generated by this programme in four seconds, after which their sum is shown in two seconds.
The Flat Sequence structure was applied in this example. When there are numerous frames, the Flat Sequence structure may consume a lot of room while still displaying all the frames (steps) in block diagram. The Stacked Sequence structure is an alternative. The frames are still sequential in the stacked sequence structure, however they are stacked one on the other. We choose the displayed frame using the Selector Label.