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Labview Interview Questions and Answers
Q1. How Do I Validate a Labview Application?
Ans. To certify a LabVIEW application, you need to demonstrate similar development practices to any of the programming languages. By this, you can make sure that any kind of risk associated with the application has been adequately mitigated.
Q2. How do I Perform Static Code Analysis on Lab-view Vis?
Ans. To perform Static Code Analysis on Lab-View, one can simply take the help of the NI Style Guide. Apart from this, Lab-View has also offered its VI (Virtual Instruments) Analyser Toolkit which can be used to automate the entire process. By using the Analyser Toolkit, you can easily detect all the improper coding techniques used during the operation that can detract from an application’s maintainability and performance.
Q3. What Is The Difference Between Local Variable And Global Variable In Labview?
- Ans. Local Variables: Local variables can be found in the structures palette of the Block Diagram (BD) and are used to make a connection with any control or indicator. If you place a local variable in a block diagram panel, you will see a question mark symbol at the top end of it. Now, you can easily connect it with any indicator/control by just right-clicking on it and choosing ‘Select Item’. Apart from this, you can also create a local variable by right-clicking on the indicator/control either in BD or in Front Panel and selecting ‘Create Local Variable’.
- Global Variable: Global variables can be used to pass and access data among several Virtual Instruments (VIs). The global variable looks like a question mark with a globe symbol after placing it on the Block Diagram. If you create a global variable in any of the LabVIEW Virtual Instruments, the LabVIEW engine will create ‘global variable vi’ at the same time in the following directory automatically. Moreover, you have to keep in mind that only the front panel exists of the global variable.
Q4. What Are The Advantages Of Labview?
Ans. Labview comes with a lot of advantages associated with it, that can simply be seen in the following points mentioned below:
- Graphical User Interface (UI).
- Hierarchical design and modular design.
- Drag-and-drop functionalities.
- Professional development tools.
- Multiple high-level development tools.
- Preserves investment and reduces cost.
- Instrument and connectivity control.
- Scalability and flexibility.
- Visualization capabilities.
- Distributed development.
- Compiled languages for fast execution.
- Rapid development with express technology.
Q5. What are the two panels used in LabVIEW programming?
Ans. There are basically two panels used in LabView programming, which can also be termed as the building blocks of it. Kindly take a look at these below-given points to check out both panels used in the LabView:
- Front Panel: It is the User Interface of your LabView.
- Block Diagram: It is the part where all the programming part is carried out.
Q6. How do I document graphical code in LabView?
Ans. Code descriptions and comments can simply be attained along with the print out of codes by using the ‘VI Documentation’ option available in the LabView print menu. Apart from this, you can simply use the NI Requirements Gateway for more sophisticated documentation. This will provide trackable links to the specification documentation.
Q7. What assurance do I have that LabVIEW is a high-quality software product?
Ans. LabView is a software built by the National Instruments, which is operating under ISO standards since 1995. Moreover, in 2005, Lloyd’s Register Quality Assurance Inc. approved the National Instruments as an ISO 9001:2000 i.e. latest standard for effective quality management practices.
Q8. Can I map requirements to LabVIEW code?
Ans. Yes, you can easily link the requirements specifications with the help of NI Requirements Gateway. This application allows you to trace the aides and requirements during the process of impact analysis whenever any kind of modifications are required. Apart from this, you can also get an insight into valuable metrics like requirement coverage by using this tool.
Q9. What are the features of Labview?
Ans. LabView packs a lot of fascinating features that can make your developing experience even more enjoyable. Some of its marvelous features can be seen in the below-given points:
- It comes with support for RS485, RS232, GPIB, VXI, PXI, and plug-in DAQ devices.
- It offers easy interfacing with RF and additional hardware by using different drivers offered by NI.
- It is blessed with TCP/IP networking and ActiveX bull, which means you can easily create executable applications and shared libraries.
- Interfacing with C and .net programming languages.
- Easy to use Graphical User Interface (GUI) based on drag and drop functionality.
Q10. What is a Shift Register? How it is implemented in LabVIEW?
Ans. Shift Registers are basically used to transfer data from previous iterations via the loop to the next iteration. It can be used by right-clicking on the ‘for loop’ structure in the LabView block diagram panel.
Q11. What is a State Machine in LabView?
Ans. A state machine is one of the fundamental parts or architectures frequently used by the LabView developers to build applications.The node where you are allowed to write mathematical expressions and formulas just like C coding. Mixed data types can be combined and passed from one place or file to another in LabView by creating a cluster of choice. Clusters basically group the data elements of mixed types, like a bundle of wires in a telephone cable. Each wire in the cable represents a specific element of a cluster.
Q14. Is there any simple code in LabView to reset all parameters at a default value for each time of execution while using Matlab scripts?
Ans. This kind of problem occurs sometimes when your program is working fine with every single run but faces some assignment and resizing problems after changing the condition. To resolve it, you can simply put another Matlab script code at the end of the program sequence and set all the variables at zero. Apart from this, you can also try right-clicking on the variable, select the ‘Data Operations’ option, and then select ‘Make current value default’. This will make your program run without causing any issues.
Q15. Is it possible to interface Labview with JAVA GUI?
Ans. Yes, you can interface Labview with JAVA GUI, however, you will have to follow the below-given steps to make it done:
- Firstly use TCP/IP to communicate between Java and Labview.
- Then simply build DLL from your Labview code and call it using JNI.
- After that, implement web service using the LabVIEW and call it using Java.
Q16. What kind of files can we use apart from .txt as input in LabView?
Ans. You can use a lot of file types from ASCII files to binary files. You just need to make a proper reader or use the appropriate VI for this. Moreover, you can also use the XML files as the software also comes with an XML parser for it. Apart from this, you can simply check out the LabView online help document to get all of your answers.
Q17. How can we add channel names to an LVM file?
Ans. To add a channel name, you can simply use the ‘Set Dynamic Data Attributes’ Virtual Instrument.
Q18. How can we dynamically create and open a folder for every iteration to save the data in LabView?
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Ans. You can simply use the Create Folder virtual instrument for this task, which is available above the list of files and directories in the file dialogue box. It will simply create a folder without saving a file. Moreover, you can check out the detailed description of this via the official webpage of the company.
Q19. Is LabView a recommended platform for a live streaming system?
Ans. LabView is a great platform, however, if we talk about a live streaming system, it is not the best in market solution. You will not get satisfactory results if you use LabView for many live streaming systems like infrared eye-tracking systems etc.
Q20. How can we modulate (AM) any sound or voice files on LabView?
Ans. LabView is self-capable of reading sound files directly from your sound card to your computer as well as opening an audio file. Moreover, you can also try implementing an AM modulator by using single mathematical operations. For example, you can use the following equation for low pass signals:
XAM(t) = A(1+mx(t))Cos wct
Here, m is the modulation index, who is the carrier frequency, x(t) is the message and A is the carrier amplitude.
Q21. How can we normalize the EMG signals with respect to mean by using LabView?
Ans. After collecting all the data in CSV files, you will need to follow the steps given below to normalize an EMG signal with respect to mean:
Read the data in terms of an array. Check out how to do it via the company’s official page.
Get the array’s size. Check out how to do it via the company’s official webpage.
Sum all of the array’s elements. Check out how to do it via the company’s official webpage.
Dividing one by another will get you the mean of the desired signal. Now, simply subtract the mean value from all the elements of the array and you will get the normalized signal.
Q22. In biosignal applications (EMG), will it be good to use ‘Average Rectification Value (ARV)’ or ‘ABS’-function for full rectification using LabView?
Ans. It completely depends on what you desire to do with your rectified signal. The ABS function will only transform all of your negative values into positive ones. Whereas, the ARV will also add another treatment as taking the mean over a time window in order to smoothen your rectified signal. Generally, we need to do a bit of smoothening after the rectification of EMG. Hence, ARV can prove to be a good option in this case by choosing the right time window. However, whether you choose the EMG or ARV, you must always remember to remove the DC offset from your EMG by subtracting the mean of your raw signal.
Q23. Does LabView decrease the speed of the microcontroller?
Ans. Yes, your microcontroller will work a bit slowly if you are using the LabView platform in your system.
Q24. How can we make cyclic programs in LabView?
Ans. To make a Cyclic program, you will need to use the For-Loop function. You can understand the working of For-Loop via the official webpage of the company.
Q25. Can we use the Biomedical and Spectral Measurement Toolkit for LabView 8.5?
Ans. Yes, you can easily use the Biomedical and Spectral Measurement Toolkit for Labview 8.5. You will just need to check the version of your toolkit for the compatibility with your LabView platform.
Q26. Can LabView read excel data continuously from Etap Software?
Ans. You will need to check out whether Etap is offering API for that particular role or not. If there is no such kind of API, you can simply let the Etap dump data to any file. After that, you can simply make a code in LabView to read data from that specific file. For this, you will have to build a constant microampere current source yourself and then use the LabView devices to sense the voltage drop.
Q28. Is it possible to perform real-time image and video compression using the LabVIEW-FPGA module in LabView?
Ans. Yes, you are allowed to perform real-time image and video compression using the LabView-FPGA module. You just need to write the VHDL code and compile as well as load it into FPGA.
Q29. How to generate two channels of digital output from one PWM signal in LabView, one for the heater and other for the cooler?
Ans. You can easily use the relay’s NO & NC contacts for cooler and heater. However, there can be a case when one wants to be neither warming nor cooling, in such case, you will have to prepare a code for it.
Q30. How can we resolve file space issues in CDAQ Controller with LabView Test System?
Ans. If the in-built storage of your system is completely filled up, there are basically three ways by which you can save your test data:
- Save to a USB flash drive
- Save to a network share
- Save to an SD card
Q31. What is the “Code Width” of an input signal and how do we calculate it in LabView?
Ans. The device range and resolution of a measurement device showcase the smallest detectable change, which can also be termed as the code width of the input signal. Smaller code width will result in precise measurements. You can easily measure the code width by using the below-given formula.
code width = device range/ 2resolution
Q32. What is the difference between CIN and CALL library?
Ans. CIN is basically used to call external c-functions, whereas, CALL library node is used to call the dlls.
Q33. Which type of Virtual Instruments in LabView does not have a block diagram?
Ans. There are basically two types of Virtual Instruments available in the LabView that do not have a block diagram. They are:
- Global Variable VI
- Polymorphic VI
Q34. Which LabView Add-Ons, Drivers, and Toolkits are available for the LabView 64-bit version?
Ans. The LabView 64-bit doesn’t support all the toolkits supported by the LabView 32-bit. Moreover, the support also varies according to the operating system:
- Windows 7
- Windows 8
- Windows 10
- Mac OS X
You can simply check out all the details related to the LabView Add-Ons, Drivers, and Toolkits for each operating system.
Q35. Can we run a VI written with LabView 32-bit on LabView 64-bit and vise Versa?
Ans. Yes, you can easily run your VI written with LabView 32-bit development system, in your LabView 64-bit system and vice versa because the code is not compiled until you run the VI.
Q36. Can I build a 32-bit version executable from the LabView 64-bit application builder?
Ans, No, currently there is no facility available to create a 32-bit version of an executable by using the LabView 64-bit application builder.
Q37. Can LabView be used to program a PLC?
Ans. No, you will not be able to program a PLC by using LabView. However, you can read and write to your PLC code by using a LabView application. Hence, we can say that a LabView application can be used to write a control loop setpoint to a PLC, and read back the system response.
Q38. Can we create PWM signals in LabView for controlling the speed of an Induction Motor?
Ans. Yes, you can use the DAQmx to program a PWM signal if you are using a product from the RIO or DAQ platform (i.e. cRIO, cDAQ, myRIO, roboRIO).
Q39. What is LabView SignalExpress?
Ans. LabView SignalExpress is basically the newest member of the National Instruments LabView family. It simply extends the acquisition, analysis, and presentation capabilities of LabView to the applications that do not require programming.
Q40. What LabView platforms/versions support web services?
Ans. The National Instruments introduced support for web services in its Labview Real-Time Targets and LabView 8.6 for Windows platforms. The web services runtime engine in 2009 and 8.6 is loaded and run with the help of LabView built-in web server. Moreover, the webserver is also available to be used on Linux and Macintosh versions of the LabView, but without any availability of web support. Notably, web services development requires a windows version of LabView 8.6, 2009, or 2010 coupled with a student, full, or professional edition license.
Q41. How can we programmatically build and deploy any web service?
Ans. You can easily build and deploy web services either by using the project tree or by using a VI offered by LabView. LabView offers G APIs (Google APIs), which can be used to open a project and every member defined within the project. You are also allowed to open a project programmatically by using the invoke node. Moreover, you can also access the targets defined in a project using the property node.
Apart from this, LabView also offers VIs, which are capable of creating a build specification defined on every target. You will get many methods with the invoke node by which you can deploy the build specifications. Furthermore, libraries included in a project can also be deployed through an invoke node using the ‘Deploy Library’ function defined in the application class.
Q42. How can we remotely invoke a web service from G-based applications?
Ans. You can easily invoke web services in LabView 2010 by using the LabView HTTP Client API. You will not get this API compatible with LabView 8.6 and 2009. To access this particular API, you can simply select Functions Palette > Data Communication > Protocols > HTTP Client. Moreover, the SSL support (HTTPS) for an HTTP client needs the LabView Internet Toolkit 2010.
Q43. How can we add MySQL functionality in LabView?
Ans. You can easily use the Database Connectivity Toolkit to add the MySQL functionality in LabView. However, if you are using the LabView 2017 then you must take a look at the LabSQL. It is a tool that allows the connection of a MySQL database without the NI’s LabView Database Connectivity Toolkit.
Q44. How can we transfer data from Python to LabView?
Ans. You can use the Command Line Interface to send the desired information from an existing Python script into LabView code. LabView can be used to execute a python script via command line and receive feedback from that command-line interface.
Q45. How can we change a default recording device using LabView?
Ans. To change a default recording device using LabView, you can simply follow the below-given instructions:
- Tap on setting
- Select my device
- Choose difficult device
- Select and activate
Apart from this, you can also choose to visit Control Panel > Device Activity > Difficult Setting.
Q46. How can we make a waveform chart in LabView?
Ans. To build a waveform chart in LabView, you will have to include both the arrays in a cluster and then simply use an XY Graph. Moreover, you can also choose to take a look at the official NI documentation related to the XY Graphs. However, if one of the axis is timestamps, you can take t=0, so that you can save memory if you are using a big amount of data. You can also check out the official documentation made by the National Instruments.
Q47. How to get a column selected by default for a multicolumn list box in a LabView VI?
Ans. You can simply wire a numeric constant to the multicolumn Listbox. Moreover, we recommend you to make sure that you are performing this task where you already know that it will be executed as soon as the VI is called.
Q48. How can we get all of the windows services in LabView?
Ans. You can get all the windows services in LabView by using the following code string into the System Exec.vi:
“sc queryex type= service state= all”
The string must be used without quotes. This will get you all the windows services in your LabView.
Q49. How to implement the N-Dimensional nested loop in LabView?
Ans. You can easily implement the N-dimensional nested loop in LabVIEW with the help of a recursive vi. It simply pulls out the 0 indexes of the array and loops over the min/max/delta of element 0.