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LabVIEW topics

LabVIEW topics

Published: Sun, 18 Feb 2018 01:30:33 GMT2018-02-18T01:30:33Z


How to create custom subVI

Sun, 18 Feb 2018 00:36:37 GMT2018-02-18T00:36:37Z

Hello all,

       I started searching if its possible to create a subVI capable of changing its own inputs/outputs based on

selector of its own. For example, the main input of this subVI is a CONTROL Selector (like an ENUM Constant)

and when I select one of its options, automatically the subVI enables and shows certain input/outputs that

corresponds to the option select. So, inputs/outputs of subVI will change when different option is selected.


Does anyone know if this is possible? If it is, can you share the knowledge of how to do it? I'm debugging and

a program, and this will come in handy.


Thanks to all, I appreciate your help!.


Timeout in waveform graph(cut out some data from chart)

Sat, 17 Feb 2018 19:02:59 GMT2018-02-17T19:02:59Z


I prepared drawing data from binary file to mixed waveform graph,

and honestly, I have no idea how to mark timeouts of signals(for example if the devices is off for some time during saving data to binary).


Client wants me to mark a timeout(time without communication with the module) as I show below(image) anyway, anybody knows if it possible??


All what Ive tried so far changed entire plot color. Is it possible to change only the part of the it?

I dont want to draw second plot marked as black to cover it... and the client doesnt want to agree to take data to zero as showed below


Now I am wondering if I should try with Xcontrol(but I dont believe to find solve it in that way)


 If it is impossible I am ready to write it in c# or other language and import as .net, but it will take a lot of time to make it from the beginning. Labview costs too much to use other languages apart from it;p.


best regards,


Using PID with a quadrature encoder to control angle

Sat, 17 Feb 2018 18:34:58 GMT2018-02-17T18:34:58Z


my team is trying to use a PID with a quadrature encoder to control how much our robot turns. 

Does anyone have any example code we could use to start? Note: We don't have NI-DAQmx.

Inverse Z transform

Sat, 17 Feb 2018 13:34:08 GMT2018-02-17T13:34:08Z


Please help me to implement the below equation in LabVIEW without using math-script module.

1 + 0.41 Z^-1 + 0.33 Z^-2 / 1 - 1.53 Z^-1 + 0.87 Z^-2


Thanks in advance for your help.

myRIO ground

Sat, 17 Feb 2018 03:22:40 GMT2018-02-17T03:22:40Z

Hi all,


I just want to ask if there is a difference between the AGND and DGND ground pins of myRIO. Are they the same? Or there is a specific or special applications for these pins?


Thank you.

Attaching a Physical Switch to start/stop Analog Data Acquisition

Sat, 17 Feb 2018 00:17:05 GMT2018-02-17T00:17:05Z

Hello Everyone,


I am using an NI 6002 to gather voltage data across two channels. I want to attach a switch to the system allowing me to write data by pressing a physical button. Write data when the physical button is pressed. Stop writing data when the physical button is released.


It is my understanding that I cannot have digital and analog together in the same task so I separated them to their own respective tasks. The NI 6002 is specified to 5V, so in order to trigger the system I have supplied the 5V though a battery. Here is the switch circuit I used where the light bulb in Digital Channel 0. When I pressed the button it does not write to my VI. Instead I get error Property Node DAQmx Trigger (arg 1) in DAQmx Start Trigger (Digital Edge).vi:3930001.

I think I am super close, but I just can’t determine what I am doing wrong.


Attached is my VI

Any advice would be appreciated!


Plotting data from text file

Fri, 16 Feb 2018 23:24:20 GMT2018-02-16T23:24:20Z

Hello, I started using Labview from few days and my first need is to plot some data reading it from a text file.

Attached an example of data file I need to read and plot.

Thanks for helping me.


VISA Serial configuration

Thu, 15 Feb 2018 20:55:33 GMT2018-02-15T20:55:33Z

Hello all,


I'm trying to run the Simple from the Serial.lvproj from the examples included in LabVIEW 2013. I am trying to connect to the COM1 port on my computer, which shows up on the windows Device Manager.


LabVIEW gives the following error:

"Error -1073807342 occurred at Property Node (arg 1) in VISA Configure Serial Port (Instr).vi->Simple" with "Possible Reason: VISA:  (Hex 0xBFFF0012) Invalid resource reference specified. Parsing error."


 I installed the VISA version 16 drivers and I can see the com port in the device manager and I can connect (and disconnect) from COM1 using Realterm (serial terminal program). The one thing that seems off is in NI MAX under Devices and Interfaces there is a line with a yellow warning symbol that says "No VISA resources found".


Do serial ports need to appear in NI MAX to be able to be used in LabVIEW? If so is there anything special I should do to get them to appear in MAX? I have a built in serial port as well as a USB serial port and I have been unable to move past this seemingly very simple step of recognizing and connecting to a serial port.

Writing PWM data to analog using FPGA

Fri, 16 Feb 2018 19:07:20 GMT2018-02-16T19:07:20Z



I am working on a project to read the period of a PWM signal using FPGA. I am transferring that data to the host(RT) to calculate frequency and then convert it into an analog signal to write it on an analog channel in RT.


However, it is not writing anything to the analog channel. Can somebody suggest a proper method to do it, I just want the latest data because the frequency will remain same, so there is no need to buffer? Also, if I can know that what is the possible cause of the error in my VI?



Kashish Dhal

set coordinate system using NI Vision Assitant

Fri, 16 Feb 2018 18:14:10 GMT2018-02-16T18:14:10Z

Hi I have 2 questions regarding NI Vision Assistant, I am getting the coordinate position of a ball using circle detection. 1) How do I configure the system so the reference point (0,0) is on the bottom left corner instead of the top left corner?  


2)Also,  How can I output the normal image after it has been processed in the NI Vision Assitant? It seems that it is going through every single step and I cant see the object position when running it. 


Thanks in advance



What is this symbol?

Fri, 16 Feb 2018 14:58:21 GMT2018-02-16T14:58:21Z


can somebody please tell me what this symbol is for?

Best regards

Event case not catching value change EVEN WITH value signalling node

Fri, 16 Feb 2018 14:50:51 GMT2018-02-16T14:50:51Z

Afternoon all,


Sorry if this has been covered before, but I've spent a while searching the forums and come up none the wiser.


I understand that programmatically changing a front panel object doesn't generate an event unless you use the Val(Sgnl) property note, but why isn't this picking anything up even with one?


There's no other event structure in use, front panel locking is off, and the new value does go to the front panel object - the event structure just doesn't seem to notice.


What am I missing?



Event structure for the disable property node

Fri, 16 Feb 2018 14:18:47 GMT2018-02-16T14:18:47Z

Afternoon Gurus,


I am writing a piece of code which has several parallel event structures, each with several cases embedded. Within 3 or 4 of these cases I need to enable and disable many numeric controls. Always the same ones to the same state.

Rather than have a disabled property node for each controller in each case, I was thinking of having a new event with one set of the disabled property nodes in and then use a FGV as the selector (enabled, disabled, disabled and greyed), which is set in the cases. Is this a good way of doing this or is there something neater. Attached is a PNG which is just a simplification of the problem.


Mucho ta-ness!

Calculate frequency of each pulse from encoder

Fri, 16 Feb 2018 13:56:43 GMT2018-02-16T13:56:43Z

I am trying to calculate the frequency from an encoder, but I want the frequency for each pulse, and not just the average frequency so that I am able to find the percent difference between the max and min values.  By creating a waveform from the array and the time between samples and using extract multi tone I am able to get 3 frequency values, but I need a larger sample size to have reliable data.

Maximum number of shift registers/feedback nodes per a loop

Fri, 16 Feb 2018 13:10:55 GMT2018-02-16T13:10:55Z


I'm working on porting code from an embedded system to LabVIEW. I need over 60 variables to be held in memory (via either shift register or feedback node). I use both as I read they gave same performance and since I don't need other than previous variable value (global scope in text based programming).


My problem is, once I added like 40 variables, the latest added value started to affect the update of others (some variables started to hold same value after few iterations). I checked the code several times and it is supposed to work. It is certainly weird behavior. All variables are initialized.


Just needed to point out that I use formula node with those shift registers and feedback node as an intermediate step before porting all code to LabVIEW.


So, is anyone aware of the maximum number of shift registers allowed either generally or connected to formula nodes? Thanks


How to make instrument drivers using dll file of the instrument control software?

Fri, 16 Feb 2018 11:50:57 GMT2018-02-16T11:50:57Z

Hello everyone,I am still new to labview and I am currently in need to make Labview drivers to control our injection set(ORTS32)..I tried to build VI's to control this instrument

but I am still struggling to establish communication with the instrument.I have attached (see the zip folder) the VIs that I developed as well as all necessary information.e.g instrument datasheet,dll files etc


Please help on how to build the VIs successfully.

Global Variables and X-net problems?

Fri, 16 Feb 2018 11:05:21 GMT2018-02-16T11:05:21Z


I made a program that take some frames from a .dbc file and change some parameters in it. I save it into a global variable,but when i use this variable the values are not correct(actually they are from main database,unmodified). In A picture you can see the modify process and at the end i write in a global var and i also do a verify to see the modify values and they are good. But in the B i use the same global variable and the values are not correct. In C you can see the output of A and in D the output of B. Anyone have a idea why this happens and how can be fixed? 

Thank you

Exporting Data with Multiple Columns in excel using Write Delimited

Fri, 16 Feb 2018 10:50:15 GMT2018-02-16T10:50:15Z



I am trying to export data into an excel file and I found that it is possible by using the Write Delimited However, I would want to insert the data in two columns as shown in the code attached. When I wire this 2d data into the vi function, I was able to export the 2d array data in csv format (also attached). But, the columns of the 2d array are just separated by commas(,) and are stored in just one column. Is there a way wherein each columns of the 2d array from LabVIEW will also be separated by columns in the excel file?

Saving data in USB in the real time system

Fri, 16 Feb 2018 10:24:48 GMT2018-02-16T10:24:48Z

Hallo everyone,

I am trying to save my data in USB in the real time system VI. My data is coming from the FPGA around 2 KHz. So in the real time system I put a Timed loop with source type- 1MHz clock and a period of 4000 us. So data is saving in the USB in CSV format. But some data is always missing. I put a Square wave generator at 1.5 Khz in the FPGA VI and counting the event. When the counter is 40, I am counting the cycle. From the save value, I can see that some cycle is always missing. For example, If one cycle is 200 then the next cycle value is 220.

To connect the FPGA with RT VI, I am using Open FPGA VI references and passing it to the Read/Write control.

How should I program so that all the values are saved in the USB? I am pretty new in Labview.

Thank you.


Malleable VIs with parameters

Fri, 16 Feb 2018 09:54:08 GMT2018-02-16T09:54:08Z

Hi All,

I have a need of parametrizing the malleable VI, or to be more generic any inlined SubVI.
The basic question is: is it possible to access the BD constants of the malleable (inlined) SubVI (with scripting for example) and store there different data for each instantiated malleable VI (like with the express VI)?

Are there any other methods of achieving what I need?
The example use case would be (it is not my use case, it is just an example (image) ): instead of connecting constant to the Stall Data Flow.vim double click it and set the desired delay.