"Write to measurement file" in labview doesnt show time instants of the waveform

Hi
I am trying to write my data into a file. I am using the "write to measurement file" for this purpose. But, the file shows only the magnitudes of the input waveform and not the time instants.
Can someone help me with this.
Thanks
Vijay Chand Ganti

Hi
Thanks for ur reply. I tried using the "unbundle by name", but thats only helpful for a cluster of elements.What i need is to
get the time instants of an analog signal (to verify its sampling rate).
I am using the example under NI example finder-->Analog Input R series.
Mine is an FPGA application and so im using the R series. I am anyways attatching the VI which i modified for my use.
Attachments:
Analog Input (Host)2.vi ‏375 KB

Similar Messages

Write to Measurement file wil not write data daily

I have been using the Write To Measurement File express VI to record daily values. The express VI is no longer saving daily files or is checking for file size. WTF. Does anyone have a more bullet proof way of saving data daily with a single header for the day?
Thanks,
Matt

MS UCD wrote:
Ravens Fan,
So to clarify, I meant local variable instead of shared variable. Shared variables will come into play when I construct the real-time embedded program on the cfp-2120 controller. Thanks for the clarification. So are you on the clock for all this?
Sometimes yes, sometimes no. Since today is a holiday, I'm off the clock.
Anyways, so if I need to have the user see the values on the front panel and also record the values later, how do you suggest one does such a thing other than writing an indicator and then making a local variable that is then recorded?
The local variable has nothing to do with recording the values later. It is just a way of accessing a control or indicator in more than one part of the program. If you used shared variables (and I think you would need to have the DSC module to have this functionality), you could write to the shared variable and have it set up to log its values to the Citadel database. It is a built-in method of logging that just requires configuration of the shared variable, no additional programming would be needed. Otherwise you will need to add the code to write to a log file like you are doing now.
The new/old mechanism for checking the date has brought the adequate functionality I was looking for- mainly new files for each day.
With respect to the race condition you mentioned, could a sequence structure be used to write the local variable to the output array? In essence, I would calculate the scaled values and then write them to the data array. Another solution could be a control in the last case that then is used to initiate a case structure in which the shared variables for the data acquisition iteration are then recorded in the output array.
A sequence structure (and a flat sequence is preferable to a stacked sequence for code readability and maintainability) would guaranteed that one section of code completes before another begins. However, it is still preferable to use wires. Wherever you are wiring to a local variable, just send the wire to the border of the while loop. Feed the wire from that tunnel to the build array function and eliminate the local variable that you are reading there. Your case structure in a while loop is really just functioning like a stacked sequence structure. Every iteration of the while loop executes the next case in the case structure. If you are sequencing through the data values in the same order that you are building them into an array outside of the loop, you could actually build the array element by element inside each case structure and use a shift register on that array to carry the data from one iteration of the while loop to the next. Then once you while loop is done, the array has already been built. If by chance you are acquiring the data in a different order then you want to build it into and array, then the array functions could get much more complicated inside the case structures. But you could initialize the whole array before the case structure, and use replace array subset to replace each specific element as you acquire it.
I am interested in the producer/consumer arrangement you speak of. Do you have an example you could send me that shows this operating?
Go to File then New.... Look under frameworks, design patterns, and Producer/Consumer Design pattern (Data). Also search the forum for producer/consumer and I'm sure you'll see plenty of examples.
As for the Time Signal controls being located in the Labview abyss, what can I say? Every learning experience has a few bugs. ; - ) If the Time Signals are constants what effects on the time in the chart will this have?
Since the time controls are way off, I assume that the program user will never actually go out into the space of the front panel to find them and change them during the execution of the code. (I am also assuming that those controls never get changed programmatically by writing to a local variable or property node or they are not part of the connectory pane where this VI is called as a subVI in another one that passes in a time stamp on every call.) If they never change, then they are effectively constant. Changing them into constants would clean up the code and make it slightly more efficient, but would not appear to execute any differently.
Thanks for helping this novice out!
Regards,
Matt

Write to measurement file at every n iterations

Hi guys,
I would like some help with saving data in labview 2010 SP1 (base development system). I am using a "Write to measurement fil express VI" inside a while loop and the data out from the DAQmn Read is wired to the signal in of the "Write to measurement fil express VI".
The way I have wired it is the VI saves the data as a text file after it has recorded 100 samples (the nuber of samples to read in this case was set to 100). I would like to know if there is a way to control the rate at which the express VI saves the data. As in, I want the express VI to save the data at specified time interval or at every nth iteration. I have attached the main VI and its 2 sub-VIs for reference. Please let know if anyone can help me resolve this issue. Thank you for your time and inputs in this regard.
Raj

Robert,
First, you must understand that the above code resides inside a loop. The blue square i terminal is known as the iteration terminal. It provides the current loop iteration count, starting from zero.
The first input (x) to the Quotient & Remainder Function comes from this iteration count (i) terminal of the loop.
The second input (y) to the Quotient & Remainder Function comes from the control N.
We wish to write to the measurement file every N iterations of the loop. If we take our current iteration count (i) and divide by our desired N, every Nth iteration of the loop, the remainder will be zero. For all other iterations, the remainder will be non-zero.
That being said, we check the remainder and compare it to zero. If it is zero, we will send a True value to the Enable terminal on the Write To Measurement File Express VI. Any time a True value is sent, we will write to file. Anytime a False value is sent, nothing will be written to the file.
The green new_file input on the Write To Measurement File Express VI is used when the "Save to series of files (multiple files)" radio button is selected in the Configure dialog box of this Express VI. When "Save to one file" is selected, this option does not apply, and so it is not included in the input list, which is why you are not seeing this.
This new_file input is used to tell the Write To Measurement File Express VI when to start writing to a new file.

Strange data saved by write to measurment file

Hi all,
I have developed a simple program that permits to visualize data from a channel, but it records data, just when the saving data button is pressed. Data are saved through write to measurment file, but unfortunately there is something wrong since the saved data is strange. In the attachment there are the VI file and the saved data.
As you can see there are several header and dates are strange (i.e. the saving date is 23/12/1916) and I get much more sample than I should have. Why do I get this?
Any suggestion is appreciated.
23/12/1916
Solved!
Go to Solution.
Attachments:
simulated_data.xlsx ‏1426 KB
read a channel and save data.vi ‏63 KB

Your many headers may be because of this:
Beginner? Try LabVIEW Basics
Sharing bits of code? Try Snippets or LAVA Code Capture Tool
Have you tried Quick Drop?, Visit QD Community.

How to populate column titles for y values when using Write to Measurement File Express VI with a tab delimited text-based .lvm file?

The .lvm file generated by the Write to Measurement File Express VI includes column heading titles for the y values, but they are a default value of "untitled". See attached example of a sample file when opened in Excel, the values in question are highlighted. Is there a way to specify the column titles when the file is written?
This is a similar question to this posting, which received a work around response to use the Write to Spreadsheet File.vi, rather than a solution when using this VI.
Message Edited by Hightop Raven on 05-02-2007 03:37 PM
Attachments:
column_titles.gif ‏13 KB

Sorry for the late reply. I was out of the office Friday.
You can do it, but the code can get rather ugly. Under the hood, the dynamic data type (the dark blue wire) is an array of waveforms. In your case, the scalar values you convert to a dynamic data type are being converted to an array of waveforms, each waveform having one element. You have two options.
Explicitly convert your scalars to one-element waveforms (t0=0, dt=1) and add the title before conversion to a dynamic data type.
Convert your dynamic data type to an array of waveforms and loop through them to add the column labels. The conversion blocks are in the Signal Manipulation Express palette.
I would recommend 2, since it is the easiest to add. It is also the easiest to run only on the first iteration. Just put a case selector around the loop, wire the selection to the While loop iterator, and set the case containing the label code to 0. The default case simply passes through the dynamic data.
My apologies for not including a screen shot. I am in the process of upgrading my machine and can't run LabVIEW. If you need one, let me know and I can post one tomorrow.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Help with saving time stamps to "write to measurement file" excel format.

I am having problems saving the timestamps from my data to the write to measurement express vi for excel. My incoming data is converted from dynamic data to a 1d array for processing, which I understand you lose the time stamp data. I added a new array for time stamps but this array then cannot be converted back to the dynamic data that is requested to go into the write to measurement file express vi. I would prefer to leave the data in an array to be saved rather than converting it to a waveform so is there any way to add the time stamps from my 1d array back into the write to measurement file?

I set it up to build a waveform now but I am still having issues with it saving the correct timestamp. The time just incriments for every second (as it did before converting the dynamic data to the waveform). I attached a screenshot.
Attachments:
waveform.png ‏36 KB

Labview 9.0: Error 1 occurred at Write To Measurement File

Hi
Our University recently got the latest version of Labview (9.0 32-bit) which I installed today.The labview file I am using (my6008v6.vi) used to work fine with the older version (8.5 i think). My write-to-file VI is enabled at certain time intervals in order to log data. As soon as it is enabled for the second time I get the following error:
Error 1 occurred at Write To Measurement File->Copy of murray6008v6.vi
Possible reason(s):
LabVIEW: An input parameter is invalid. For example if the input is a path, the path might contain a character not allowed by the OS such as ? or @.
=========================
NI-488: Command requires GPIB Controller to be Controller-In-Charge.
I made a simple file (simplew2f.vi) to test this, with a button which I can press to enable/disable the writing of data. I am able to start writing data and then stop writing data but as soon as I try resume the writing the same error occurs.
This confuses me greatly since this wasn't a problem using the old version and my Labview knowledge is minimal. Any help would be appreciated.
Attachments:
my6008v6.vi ‏214 KB
simplew2f.vi ‏64 KB

So, which VI are you having problems with? Sounds like both...
Okay... - sigh - where to start....
Well.. Let's start with a few comments.
1. Try to stay away from the Express VI. I know the Marketing guys at NI will not like me for saying so, but I am saying so. They are a nice marketing feature that Grumpy Old Men like myself do not like. They make it easy to write quick code.. And I will limit my comments to that. (It's not your fault.. )
2. The wiring on your diagram is not clear or easy to read. Yes, with additional time and double-clicking each wire I can tell where they are going. However, a rule of thumb, alway wire from Left to Right. Never right to left. And do not run the wires under objects, even the ones you are wiring to.
3. simplew2f.vi: You should put a small delay in the While Loop. I ran it three times and it wrote to the files without error. And yes, I used LV2009.
4. my6008v6.vi: Avoid wiring from the top of the While Loop. At frist, it looked like the data was coming out of the While Loop because the wires went to the left side of all the index node of the Index Array function.
You should set your Browse Option for the file path to "Files or Folders" and "New or existing". I did that and I was not getting the error message you described.
R
Message Edited by Ray.R on 03-03-2010 08:33 AM
Attachments:
pathProperty.PNG ‏13 KB

Hi am trying to save Data into a write to measurement file vi using a NI PXI 1042Q with a real time mode but it is not working but when i run it with uploading it into the PXI it save in to the file

Hi am trying to save Data into a write to measurement file vi using a NI PXI 1042Q and DAQ NI PXI-6229 with a real time mode but it is not working but when i run it without uploading it into the PXI it save in to the file please find attached my vi
Attachments:
PWMs.vi ‏130 KB

other problem is that the channel DAQmx only works at real time mode not on stand alone vi using Labview 8.2 and Real time 8.2

How to put the proper header at each column in write to measurement file (.lvm) ?

Hi,
i would like to know one thing about the write to measurement file. Can i put the proper header at each column in write to measurement file (.lvm) ? and how can i do for it ? Could you show me a way to make it ?
i am looking forward your kindly reply.
thank you so much ..
best regard,
roxy

Hi Mike,
Thank you very much for your help. It works .
By the way, i would like to ask you about setting time interval. In the pic, X_Value column is for time column
i would like to ask that when i use the write to measurement file, there got the x column that show time inside the excel file. In this column, i would like to set the time interval at every 210ms .The data may come in every msec but i just want to record the data at every 210ms . for example, 210ms-420ms-630ms ..etc. how can i set it ?
One more thing .. can i do it in graph as well ?
i am looking forward your kindly reply.
Thank you for your time.
Best Regard,
Roxy

Remove milliseconds from timestamp in write to measurement file

I'm logging data to a binary tdms file using the write to measurement file express vi. I choose my x axis to be time and see that an absolute timestamp is written with millisecond precision. I only need to-the-second precision. Is there anyway to change this default behavior?
Attachments:
remove.png ‏10 KB
remove.png ‏10 KB

Where is your data coming from. When I open the express vi to look, it looks like the time format doesn't determine that, but the
signal data cluster coming in does. So where does the data come from, and in what form?
Putnam
Certified LabVIEW Developer
Senior Test Engineer
Currently using LV 6.1-LabVIEW 2012, RT8.5
LabVIEW Champion

Capturing data using write to measurement file for encoder

hello dear,
can anyone help to check with my encoder to measure data?
i have connect the write to measurement file but when i open the .txt file,
no result appear, thanks so much for your help
Solved!
Go to Solution.
Attachments:
encoder capture.vi ‏180 KB

well, I have never used that method to write data to a file, but if you double click on your write the write LabVIEW measurement file object and look at the configuration you have selected save to a series of files. Is that what you wanted, or did you just want one file?
Jim
Jim
LV 2013

Write to measurement file pda

hi, ive been learning labview on v.7.1 and now im trying to create simple programs on labview pda 8.21.
i want to continually record a signal to text file like an lvm. i was previsously just using the 'write to measurment file' function and connecting my simulated signal straight to it. now when i try to run it in a windows 2003 mobile emulator i get the error 'subVI is not executable'
what would be the best way of getting around this? as this is a big sticking point for my project.
thanks alot
andrew
Message Edited by lav on 03-17-2008 07:47 AM

Hi Andrew,
I hope you are well. Thanks very much for your post. I have taken a look at your problem and I think it may be due to some incompatabilities between LabVIEW and the PDA that you are using. I was wondering if it would be possible for you to post the code on the forum so that I can take a closer look at it to try resolve the problem.
Thanks very much.
Kind regards,
Prashant M
Applications Engineer
NI UK & Ireland

"Write to measurement file" express VI (TDMS foormat) keeps file opened

Hello!
I am trying to use "Write to measurement file" express VI to write TDMS data obtained from DAQmx in LV2011. Each run of the same write function creates new file.
It seems that last written file remains to be opened until program stops or next file written. It has 0 size and it is not possible to access it from other programs.
Is it possible to save file immediately and close it?
Solved!
Go to Solution.

It seems, that wiring "DAQmx task" (for AI task) to "Write to measurement file" express VI does not works in my case (only in exe).
The error is the same as file not found (error code 7), but file is created. Something gets wrong inside express VI. I am unable to debug exe, so I have just disconnected DAQmx task from express VI (really don't specially need it anyway).
For sure, the same LabVIEW version and drivers are installed on target and VI is working in it as well as at dev machine.
Debug error which I had encounter is already published in the forums elsewhere. It seems that the problem is in VI without block diagram inside hierarchy. Maybe with Express VI.
PS test app writing tdms files the same way is working like a charm (without DAQmx task wired).
So, thank you for yor advices, the problem seems to be solved. Maybe I will have a look in more details about the reason of such error, but can't do it now.

Write to measurement file loses timestamp data in tdms format

Hello all, I'm using the Write to Measurement File expressVI and I have created a loop in order to be able to individually label the column headers for each data signal that I'm writing. However, while the loop is successful in doing this the resulting TDMS file that the expressVI creates ends up losing the timestamp data that is used to record the time for each row and just writes a '0' instead. The timestamp data is present before the loop that adds column headers, which I have verified by adding an expressVI just before the loop. Please see the attached code for clarification.
How do I regain the timestamp info after the for loop executes and adds column header info? Thank you.
Attachments:
Write to measurement file specify column name.vi ‏106 KB

The problem with Express VIs and with the Dynamic Data wire is that they (almost) complete obscure what is being done "under the covers". They manipulate data in ways that are unseen and often unexpected. While they allow beginners to do extremely simple tasks quickly, they can easily lead to situations such as you are discovering.
If what you want to do is to write a TDMS data file, you should probably investigate the TDMS functions on the File I/O palette. I've not used TDMS myself, but I know there are examples and documentation in the LabVIEW Help. I suspect that if you do go with straight TDMS, you will probably save yourself further problems by not bundling your four inputs into a Dynamic Wire, but making them a 1D Array (or possibly a Cluster).
Bob Schor

Write to Measurement File time column wrong starting value

I am using Write tp Measurement File express VI. I select to write one time column. The values writtent in the time column start from a value that does not seem to correspond to anything in the program -- sometimes as much as 2-3 days before the saving begins.
Can I force the starting value of time to something, or get it to write the time since we started saving, or something predictable?

Include code whenever available. Asking somebody to troubleshoot your software without any code is like asking your mechanic to fix your car without taking your car to him.
Source
I don't recommend using the Write Express VI. I recommend using the File I/O primatives because they allow for much more control over what gets written and how. Still I would expect the Express VI to be able to write time properly so I'd assume there is some kind of bug with the data being given to the function. Post some code so we can see what is going on.
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If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

"Write to measurement file" in labview doesnt show time instants of the waveform

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