Write to Measurement File Express VI: file name prompt

I am using the Write to Measurement File express VI to write some data.
Even though I have not selected "ask user to choose file" and have set a default filename, the vi still prompts me to choose a file. I tried restarting my pc and it used the default filename the first time and then went back to prompting me. I have set the default to overwrite my existing file each time, so I don't understand why I keep being prompted. If you look in the express VI the "ask only once" radio button is selected and greyed out, but I don't know why; I didn't select it.
(I have the express VI in a while loop and want it to write a line of data to the file each time the loop executes, so it's not convenient to be prompted for the filename each time)
I'm sure this is my own silly fault but would appreciate some advice
Thanks, klara
Attachments:
2PDCal_USB1v3.01.vi ‏441 KB

I'd suggest changing the mechanical action of your stop button from "Switch When Pressed" to "Latch When Released". This might be the only problem. If you didn't manually change your stop button back to false before running again, your loop would run once and stop, and you'd immediately see the file dialog from the Format Into File function. Changing the mechanical action would prevent you from needing to manually change it back to false before the next run.
Message Edited by Jeff B on 02-07-2008 08:48 AM

Similar Messages

Problem with Write To Measurement File Express VI not writing to file if file was deleted after the first call (7.1)

I'm using the Express Write to LabVIEW Measurement File in LV7.1.
I have it set to "Save to one file" and have tried both "Overwrite file" and "Using next available file name" for the "If a file already exists" conditions.
The path/filename is passed into the function.
It works fine the first time around. If the file is deleted before the function is called again, an error occurs since LV is unable to find the file.
I have had to stop and re-run my program in order to write to use the function again.
Since I am able to delete the file I assume it was closed but it seems like LV expects it to be there, even though the function was supposed to create/open/close the file... Is there any way to reset this without stopping/restarting the program?
Since my application creates several files (only one using the Express VI) I am checking for the filenames and requiring that they be deleted (or a new filename be used) before acquiring data. Everything has worked great, except for the Express VI.
Thank you,
David

Ok, I've edited the VI you posted to reproduce my error (this time with 8.0).
I added a "master stop" and "start log" button. To demonstrate my problem:
1. Run the VI
2. Click "START LOGGING" - c:\test.txt is created
3. Click "STOP" - c:\test.txt is closed
4. Delete the file c:\test.txt with Windows shell or explorer
5. Click "START LGGING" - a new c:\test.txt file should be created but instead an error is raised in the Write LabVIEW Measurement File function.
Any ideas?
Thanks,
Dave
Attachments:
Write LV Meas File 2.vi ‏96 KB

How to name columns in "Write LabView Measurement File" Express VI

Hello, I am inputting two signals into the "Write LabView Measurement File" Express VI, and although the data is recorded correctly, there is no separate header for all the y-values (I only get the X-value column labeled: X_Value), and then there is a "Comment" field right next to it. How do I name these y-value columns so that the header appears alongside the X_Value tag? Thanks.

I don't want to read from a LabView measurement file. I'm saving in a file; that's good enough. I just need to save it in headed columns. Any suggestions?
Here's a test of the program with two random data inputs, and a picture of the output.Message Edited by Doagie on 06-13-2005 01:22 PM
Message Edited by Doagie on 06-13-2005 01:22 PM
Attachments:
1.bmp ‏218 KB
2.bmp ‏405 KB

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.

"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 Express VI - TDMS file has separate "channels" for each data point

Im trying to write a VI to measure and record thermocouple data from an Advantech T/C DAQ. Using the "DAQNavi" express VI provided by them, connected to the Write to Measurement File express VI, I have managed to read in the data and create a TDMS file. However, when I open the TDMS file, each time step of temperature data is entered as a separate channel, instead of all of the channel data going into one tab. Obviously this is a huge problem as it creates hundreds of tabs after just a few seconds. Any thoughts as to what causes this?

Hi glibby,
How did you configure the Write to Measurement Express VI? Please select "one header only".
If you have your own timestamps to write, please merge your timestamp channel and measurement channels with "Merge Signals" before passing them to the Write to Measurement.
Best Regards,
Mavis

Write to measurement file will not ask for file name once as selected.

When using the Write to Measurement file Express VI. I select "Ask user to choose file" and "Ask only once" with the intention that the data from each iteration simply be appended to the chosen file.
I select "Run continuous" and the VI asks for me to choose a file repeatedly anyway instead of just appending the first file. Selecting "Write to one file" properly appends data to the file specified in the box.
Am I doing something wrong?

DianeS wrote:
Personally I can't figure out why that particular button even exists (I'm told it's occasionally useful for debugging).
I find it useful if I am creating a subVI that is supposed to be a part of another VI. No while, loop just some inputs and outputs as a function. If I want to test it out stand alone and try a variety of inputs, then Run Continuous and change the inputs, then I see immediate feedback on the outputs. Once I'm satisfied its working right, then there is no need to clean up. Just save it and drop it in the large VI as a subVI.
Beyond that, I see no need for Run Continuous.

Write to measurement file, adding column name in text file.

Hello,
Is it possible to add own column name for a text file using Write to measurement file function?
In the created file I have three different columns (I want to name them Time/Voltage/Date&Time).
Maby I should choose different write option like write to spreadsheet?

You are going to have to post some actual code if you want us to help here. Otherwise it is a complete shot in the dark. Posting an example CSV file of what you have and what you want would also be beneficial.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Samples number is not properly set with VI Express Write To Measurement File

Hello,
I have a strange problem with the VI Express Write To Measurement File.
When I generate the .lvm file the samples number for each channel is equal to 1
instead of 34 !
So when I use the VI Express / Input / Generate an arbitrary signal and I want to import
the generated signal... only one point (the first one) is imported...
I can manualy fix it by changing samples number in the lvm file using a text editor but that's a (very) dirty hack !
Here is an example of the generated LVM file
LabVIEW Measurement
Writer_Version    0.92
Reader_Version    1
Separator    Tab
Multi_Headings    No
X_Columns    One
Time_Pref    Absolute
Operator    scls
Date    2008/04/12
Time    10:35:58,322057
***End_of_Header***
Channels    2
Samples    1    1
Date    2008/04/12    2008/04/12
Time    10:35:58,323057    10:35:58,323057
X_Dimension    Time    Time
X0    0.0000000000000000E+0    0.0000000000000000E+0
Delta_X    1.000000    1.000000
***End_of_Header***
X_Value    Untitled    Untitled 1    Comment
0.000000    0.000000    20.000000
0.082000    10.000000    20.000000
0.182000    10.000000    25.000000
0.282000    20.000000    25.000000
0.382000    20.000000    30.000000
0.482000    30.000000    30.000000
0.582000    30.000000    35.000000
0.682000    40.000000    35.000000
0.782000    40.000000    40.000000
0.882000    50.000000    40.000000
0.982000    50.000000    45.000000
1.082000    60.000000    45.000000
1.182000    60.000000    50.000000
1.282000    70.000000    50.000000
1.382000    70.000000    55.000000
1.482000    80.000000    55.000000
1.582000    80.000000    60.000000
1.682000    90.000000    60.000000
1.782000    90.000000    65.000000
1.882000    100.000000    65.000000
1.982000    100.000000    70.000000
2.082000    110.000000    70.000000
2.182000    110.000000    75.000000
2.282000    120.000000    75.000000
2.382000    120.000000    80.000000
2.482000    130.000000    80.000000
2.582000    130.000000    85.000000
2.682000    140.000000    85.000000
2.782000    140.000000    90.000000
2.882000    150.000000    90.000000
2.982000    150.000000    95.000000
3.082000    160.000000    95.000000
3.182000    160.000000    100.000000
3.282000    170.000000    100.000000
PS : I also post my problem at
http://forums.lavag.org/Strange-behaviour-of-VI-Express-Write-LVM-t10570.html&gopid=44101#entry44101
Attachments:
generate_step_lvm.vi ‏119 KB

If I use the "one header per segment" option I get the following LVM file (see below)
But the problem is same !
I can't import this file in VI Express / Input / Generate Abitrary Signal (I only get one row... the first one)
I see three solutions :
- VI Express Write LVM has a bug ?
- I don't know how to use this VI Express correctly !
- VI Express / Input / Generate Abitrary Signal has a bug ?
LabVIEW Measurement
Writer_Version   0.92
Reader_Version   1
Separator   Tab
Multi_Headings   Yes
X_Columns   One
Time_Pref   Absolute
Operator   scls
Date   2008/04/12
Time   16:38:37,578
***End_of_Header***
Channels   2
Samples   1   1
Date   2008/04/12   2008/04/12
Time   16:38:37,592999   16:38:37,592999
X_Dimension   Time   Time
X0   0.0000000000000000E+0   0.0000000000000000E+0
Delta_X   1.000000   1.000000
***End_of_Header***
X_Value   Untitled   Untitled 1   Comment
0.000000   0.000000   20.000000
Channels   2
Samples   1   1
Date   2008/04/12   2008/04/12
Time   16:38:37,717   16:38:37,717
X_Dimension   Time   Time
X0   1.3899993896484375E-1   1.3899993896484375E-1
Delta_X   1.000000   1.000000
***End_of_Header***
X_Value   Untitled   Untitled 1   Comment
0.139000   10.000000   20.000000
Channels   2
Samples   1   1
Date   2008/04/12   2008/04/12
Time   16:38:37,739999   16:38:37,739999
X_Dimension   Time   Time
X0   1.6199970245361328E-1   1.6199970245361328E-1
Delta_X   1.000000   1.000000
***End_of_Header***
X_Value   Untitled   Untitled 1   Comment
0.162000   10.000000   25.000000
and so one ...

Time format in 'Write To Measurement File' express vi

Hi,
I'm using the 'Write To Measurement File' express vi to save data acquired using a PCI-6221 board and the DAQmx vi s. The acquisition is continuous.
When I set the 'number of samples per channel' property of the DAQmx Read.vi to -1 (ie, read all available samples), the time is saved in relative format. When I set any other value (ie a certain quantity of samples), the time is saved in absolute format.
Do you know why the vi does this, and if there's any way of controlling the time format ?
Thanks,
ps : I use Labview 8.0

Hi Scalpas,
I look into what I believe you are doing , but I didn't see the same results. Can you explain what datatype you are transferring to the Write to Measurement file VI? Or provide a sample of code that demonstrates the issue.
I think it might have to do with the DataType conversions when writing that file.
Sappster

"write to measurement file" specify column names

I'm using "Write to measurement file" VI to create a TDMS file from 2 and possiby more data sources. Currenty the columns are titled "Untitled", "Untitled1", etc. I would like to specify column names. Can anyone point me to an example or tell me how to do this?
Thanks,
Ron

Hi,
I've done some project with TDMS a few times and you can wire the column names (channel names) to the VI. See attachement
Kind regards,
- Bjorn -
Have fun using LabVIEW... and if you like my answer, please pay me back in Kudo's
LabVIEW 5.1 - LabVIEW 2012
Attachments:
TDMS.JPG ‏24 KB

Quickie: Write to measurement file VI, how to create new file?

I am using the write to measurement file express VI in my code and I have wired into it a control that sets the location to save the measurement file
The only problem is the measurement file has to exist first!! I cant for example, from the front panel, click the browse directory box, navigate to a folder and type in a name for the file. It just says file not found! Its like the file directory control is opening a file to save to, rather than creating a new file in that location
How can I solve this?
Solved!
Go to Solution.

Project attached
If I go in browse options what do i do? Just chose new and existing files?
Attachments:
engine.zip ‏119 KB

Binary file is greyed out in Write Measurement File express VI.

I am running labview 8.2 on Fedora 7 Core. I have also installed it on an earlier version of fedora that was in line with the supported red hat distribution. The problem is that when I try to use the Write Measurement File express VI, the binary file option becomes greyed out after the dialog box opens up. It is present for a second but it is impossible to select. When I have tried bringing over a vi written in Windows (where the binary option was available), the option is also disabled. I am trying to avoid writing the file out in lower level code since I want to use the auto file name generation available under the express VI. If any body knows a workaround or has some sample code that writes out a new file for each measurement with the date and time in the filename let me know.
Thanks

Hi Ikiller,
Is this still occurring?
Could you please provide a screen shot to show the behavior?
Thanks!!
Aashish M
Applications Engineer
National Instruments
http://www.ni.com/support/

Read from Measurement File Express VI - Time information

I need some assistance with a small problem with building reports of collected data. I don't see it very relevant, but I'm collecting data from several modules on a 9074 cRIO. I'm not using the cRIO the way it is intended, but it is perfect for my needs. Anyway, I'm collecting the different types of data in RT, then using the express VI "Write to Measurement File" with TDMS option selected and one time column only selected. Also one header, etc. Nothing fancy.
In another VI I want to use this collection of .tdms files to create an Excel report. Everything is working good however I need a time column for reporting my data. When I view the .tdms file using Excel Importer, the time column is there and perfect, with the next column a relative time (or iteration) and then columns with the signal names at top and all the data below. Perfect.
I'm similarly using the "Read from Measurement File" Express VI to get the data back the same way it went in. I have everything in it's correct place on building the Excel Report, but I haven't been able to find any way to include the first time column in my import. I can use "Get Attributes" Express VI to get the signal names from the read, but that's not going to help with the time data. How is it possible that Labview allows to put the time data there, but not retrieve it? I'm aware of the warnings that Timestamps aren't supported by TDMS file format vs LVM, but there MUST be a way to retrieve that time information if "Excel Importer" can do it.
If that time column in the TDMS file is somehow computed using the start timestamp and dt, can someone explain how to compute that for my report?
Unfortunately, I can't use the LVM format because I need to allow the users of these VI's the backup of using Excel Importer to see this data if my report generation VI is not functional.
I'll attach one of the TDMS files for illustration. The first column of the second worksheet is exactly the data I need for my report.
Attachments:
TDMS Imported.xls ‏28 KB

DylanC,
Your solution works as needed. Thank You.
I think I found a better solution though. Apparently if you convert a signal from the Express VI "Read from Measurement File" into a waveform the time data required is included, then you can convert to a string with a for loop and insert it as a row header into a table. The result gives me what I need. I attached a screenshot if someone is interested.
AWyers
Attachments:
TableFromTDMS.JPG ‏61 KB

Write to measurement file - Create or replace with confirmation

I'm using the "Write to measurement file.vi" and I want it to ask for confirmation if I try to save with a filename that already exists and then allow me to choose another file name or overwrite the old one. How can I do this?
Solved!
Go to Solution.

smercurio_fc wrote:
Ben wrote:
smercurio_fc wrote:
That Express VI does not have the capability you are seeking. ...
Help us Obe Wan, you're our only hope.
Ben
Did I misunderstand the question again?
No.
Spoiler (Highlight to read)
Your wording reminded me of the scene from Star Wars when Ben Kanobe di dthe force thing on the strorm troopers telling them "These are not the droid you seek."
Your wording reminded me of the scene from Star Wars when Ben Kanobe di dthe force thing on the strorm troopers telling them "These are not the droid you seek."
Its just Friday.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
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Write to Measurement File Express VI: file name prompt

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