Creating & Using Functional Global in LabVIEW

An un-initialized shift register with in the single run loop (Before LabVIEW 8.5 ) VI is Functional global. This VI must having Read & Write operation. Functional global is also called as LV2 global.
This is similar to global variable (Used to read & write the values among the VI’s ).
Some advantages are,
* Avoid racing in value read & write operation
* Easily used among VI’s & subVI’s
* Modification & Addition of more operation is easy
Do not set Reentrant execution property in Functional global VI because it will make racing.
The basic method for creating Functional Global is given below (See Picture)

Operation enum having Write & Read item. In write case value is stored into shift register .In Read case stored value is getting in the Value Out variable. This stored value is kept in the shift register upto the LabVIEW application is closed. You can use while loop with single run as a Functional global.

Tips for timestamp calculations

I was studied the article “LabVIEW tip: easy relative timestamp calculations” from this link.This method is very simple for calculation with Timestamp control.The addition of day,year,hour,min,sec is also done by this method .DBL data type constant with unit label is used for these calculations.See the attached picture for adding one day with time stamp control.

Creating Text Labels instead of numeric scale in controls (Gauge,Slide,Dial etc)

Controls like Gauge,Slide,Dial are DBL data type(by default) & having the numeric limits with changeable scale .If you want Text Label for Dial, Gauge… controls follow this method.
Right click on the control->select Text Labels option & Edit the Text Display which is contains the min & max labels as default. The attached picture shows the Dial control with Level 1 to Level 5 text labels.

Creating multiple Controls/Indicators in Front Panel without using any additional variables

In Front Panel multiple Controls/Indicators with same behaviour without using any additional variables is attained by Advanced ->customize option of that control (or) indicator.First select Digital Display option of the control from Right click the control ->Visible Items-> Digital Display then go to customization. Replace the Digital Display by any other control like Gauge, Meter...etc. Repeat the customization to replace the digital display of the new custom control with another control. (See Picture)

Disable the Numeric control entry field

In run time restrict the user from typing something into the entry field of the numeric control (or) String control is easily done by the following trick.
Select a "flat box" from decorations->Flat box, resize/move it to exactly cover the Numeric control user entry field and paint it transparent . Group it the flat box & Numeric control and also select “Skip this control when tabbing" option in the key navigation dialog of the control to avoid the tabbing access of the control.

Tips for getting Drive List of the system

To get the drive list of our system in LabVIEW is obtained by List Directory function which is lied in the Functions Palette -> File I/O -> Advanced File Functions -> List Directory. If you giving empty path as directory path of List Directory function you get the drive list of the computer from the directory names string array. (See Picture).It is a very cool & nice feature in LabVIEW.

Using Description and Tip option

Description and Tip is a very useful option for the controls & Indicators in front panel. Right click on the control or Indicator & select the Description and Tip option. Tip is a popup tool tip shows on run time when mouse over the Front Panel element. Description shows on Ctrl + H help window for the Front Panel element.(See Picture for selecting this option for control)

You can change the Description and Tip of Front Panel elements on run time by its property nodes.

Generating alternate numbers periodically

For getting the alternate numbers in loop periodically is obtained by Quotient & Remainder function. If u like to generate the numbers 0,1,2 periodically means connect the Loop iteration (while or for loop based on usage) terminal to Quotient & Remainder function x input & create constant 3 on y input(constant should be addition of one with last number in the periodic numbers).See picture1 for Example(four periods of 0,1,2 numbers generation).

Tips for Unit Conversion

I was studied the article " easy unit conversion " from the following link.

This method is very simple for unit conversion without using the unit label of the control.
This method uses the function - Convert Unit. (See Example)

Tips for creating Sub VI

Everyone knows the method of creating the SubVI by using wiring tool & connector pane (click on control & click on necessary connector pane terminal).The easy & quickest method for creating the SubVI is,

Select the part of the code which one you like to create as a SubVI & go to Edit menu then select the option “Create SubVI”(See Picture 1) .Now the selected part of the code is automatically converted into a SubVI(See Picture 2).

Tips for insert the function in-between wiring

Inserting the function tool in-between wires is easily done by right click->Insert->select tool from function palette. For two input function (like Add,Subtract… ) insertion in-between wiring you have two options, if you like to insert the first terminal of the function on the wiring- Right click below the wiring and insert it or you like to insert the second terminal of the function on wiring- Right click above the wiring and insert it. (See Picture 1)

Swapping the wire terminals (two input function)

If you have function of two inputs like Add, Multiply…etc , you can easily swap the input wire terminals without deleting the wires. For example you have connected x1,x2 as input terminals in Subtract function, the swapping of x2 into x1 and x1 into x2 is done by the following method,

Keep auto tool selection enable – move the mouse over subtract function input terminals and press control key you got a symbol like -8 just click it now you got swapped input terminals.

Randomly mixing the array elements

There is no direct tool for mixing the array elements randomly in LabVIEW 7.1 & below versions .Use the following method for mixing the array elements (See Picture 1)

Limit string length of the string control

In some string control using user interface applications need the limited string length option for restrict the user from entering the unnecessary strings .My method for limiting the string length is (See picture 1),

String control connected with String Subset(with length) and the substring connected with the local variable of that string control.String Subset length 10 constant denotes the Maximum string length of that control.Select the update value while typing option of the string control by Right clicking on control for run time string length control. If any other way please let me know.

Quickly entering items into Ring & Enum control

The conventional method (Right click-> Edit items) for entering the items into Ring control is uses only when you need the sequential value changes for the items. If you don’t need the sequential value changes for the items the easiest & quickest method for entering items into Ring & Enum control is,

Select Edit Text from the tools palette and click inside the control -type the item & press shift + Enter button then again enter item .

Tips for Case Structure

The Case selector terminal is accepts string,enum,boolean,integer types.If you like Case Structure connected with string should be case insensitive choose Case Insensitive Match option by Right click.(See Picture 1)

















Radix selection is also accomplished for numeric control connected case selector by Right click->Radix-> Hex or something .(See Picture 2)

Working on Compound Arithmetic tool in LabVIEW

For arithmetic calculation such as addition,subtraction etc we are using add,multiply & more tools from the Numeric palette.If many inputs are using in the calculation, the block diagram should be little bit extended by more Numeric tools & wiring. For a clean block diagram use Compound Arithmetic tool from numeric palette.By using this tool the addition & subtraction ,Multiplication & division calculations are easily accomplished without using the separate tools like Add, Subtract, Multiply, Divide.For example, Result=I1 + I2 –I3 calculation is done as per below (See Picture 1 for both two methods).

The invert terminal denotes the opposite calculation(In addition operation invert works as subtraction & Multiplication operation invert works as division ).To get invert input terminal- Right Click on the terminal and choose invert.Boolean operations is also done in that tool by changing its mode(By Right Click on the tool->Change mode->OR).

Find number of times occurring element in an array

To find the particular element occurrence in an array is easily accomplished without using any loops. The method is (See Picture 1 & 2),






























This method is work on both numeric & string array.(for more methods see NI Discussion Forums )

Converting string array to concatenated string

The conversion of string array elements to concatenated string is easily accomplished without using for loop with shift register concatenation .For concatenating the array elements into string without any delimiter is easily attained by the tool Concatenate Strings.Get Concatenate Strings tool by, Function palette->string-> Concatenate Strings
Wire the string array to Concatenate Strings single terminal and create the indicator to see the concatenated String (See Picture 1 & 2).

The numeric array elements concatenation is also possible by converting the numeric array to string array and Concatenate Strings then convert back to numeric indicator( See picture 3 & 4).

Checking the File existence in particular path

The most of the projects file creation & deletion operation is needed. On these operations file existence checking for particular file path is important. For file existence checking there is no direct tool in LabVIEW 7.1 and below versions. But its accomplished by File/Directory Info tool.

To get this tool,

Functions Palette->File I/O-> Advanced File functions-> File/Directory Info.

Wire the error out of this tool to case structure . The No Error case denotes the File is exists,if error is getting means the file does not exists (See picture 1)

Getting Application Path for an EXE

In development environment the the current VI path tool gives the path. For an EXE we are not getting the exact path. For gettting the current VI path for an EXE use property node from
Functions palette->Application Control->Property Node, The properties Application kind & Application directory are selected by
click on the property node ->Application->Kind & for next property
click on the property node ->Application->Directory Path (See Picture 1)















Connect the Application kind to case structure terminal to get the Development system,Run time System and more kinds..
Use the Directory path wire for getting current path for an EXE (See Picture 2)