Include time stamp in Write to Measurement file

Dear Experts,
I would like to include the time stamp in the data sheet I saved using a Write to Measurement file. Currently only 1 column of data was saved without the time stamp. Is there anyway I can save the data together with its time stamp in a single file (side by side column)?
Thank you.
Regards,
CYTeoh

Did you configure the Express VI to create a time channel:
Christian

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Formatting the time stamp in "Write LabVIEW Measurement File"

When I use the "Write LabVIEW Measurement File" vi to write data
the files first column contains the number of seconds since the staart of the file
How can I get the computer date and time or at least the time HH:MMS???
Tom
PS, And how can I put some sensible label on each columns in the file?

Tom,
The vi I'm attaching demonstrates how to use the computer system time for the timestamp on your LVM file. It takes a reading from the DAQ Assistant and applies a system time stamp. It's in version 7.1, but let me know if you need it in version 7.0.
As for inserting meaningful column headers, you won't be able to do that with the express vi, but you could use the regular file i/o vis to create a file like that is similar to a LVM file, but is a little more customizeable and can be formatted however you like. The express vi is meant to be a quick solution, but does not offer all the versatility of the vis on the palette. I hope this helps you out. Have a good one, Tom!
Tyler S
Attachments:
LVM_timestamp_7_1[1].vi ‏265 KB

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

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

I used "Get Waveform Components" to separate waveform data. I need to get the time stamp and write it on file as an header.

I am not able to solve the problem because I can't find an I/O vi that writes on file time stamp data. An error occurs, because of connecting different data types. How can I convert time stamp data so that I can use it as input in a write on file vi? Please, help me!

The problem with the selection seems to be that you are using two different indexing tunnels on the for loop. One of them loops over every value of the first incoming waveform, the other one over all waveforms in the incoming array. The value you wire to the N terminal will be ignored, the number of loop executions will be the minimum of your indexes. Anyway, the loop doesn't seem to do what you wanted:
- If you want to store the complete waveform: loop over all waveforms, check for the maximum of each of them and write it just like you do now.
- If you want to store only the values of each waveform that actually exceeded the threshold: You can either use 2 nested for loops to iterate over each value of each waveform. Use shift registers t
o create new arrays of timestamps / values for the values you want to store. You need to either convert the waveform to x-y-pairs (VI on analog waveform palette) or calculate your own timestamps. You might as well want to check out the "Search waveform" VI. Configure it so that value+-tolerance covers the band between your expected minimum value and your threshold value. The VI will give you the indices and timestamps of all fits.

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.
Unofficial Forum Rules and Guidelines - Hooovahh - LabVIEW Overlord
If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.

Time with 'Write to measurement file'

Hello,
I am making an acquisition waveform. The integration time is 1s divided in 128 samples. When I execute the software, the datas are stored in a text file with 'Write to measurement file'. This text file is a continuous list of 128 numbers-packs in rows.
I want to add the time column (date+hour+minutes+secondes+1/10sec+1/100sec) in front of each number acquired. (And not only in front of the first number of the 128 package)
I have don t know how to add this.
Can you help me?
Thanks a lot.
(See file attached)
Attachments:
test3.vi ‏148 KB

Also, in the setup dialog for the Write Measurement File, there's an option to include an "X Column Value" that normally holds a timestamp.
Enable one of these options and any included timestamp in your waveform will go into this column. If you don't have a waveform, you can build an extra column in your array of data points with the needed timestamp and it will work the same.
Ed
Message Edited by Ed Dickens on 02-20-2007 03:37 PM
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.
Attachments:
WLVMF Time Column.gif ‏9 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

Time stamp data write to file problem

Hello!
I'm just learning LabView, and have arrived at the stage of writing time-stamped data to text files.
This seems clear enough, however when I examine the file written to disk, I find 4 unexpected characters: 3 spaces and one seemingly random number or punctuation mark, preceding every line!
An example is:
   .2005-07-15 10:55:40.0 the value is 0.0000 cm
   .2005-07-15 10:55:40.5 the value is 1.0000 cm
The four characters "   ." are those whose origin I can't understand. I can't seem to get rid of them.
They seem to change with the input string, but not in a manner I can predict or understand.
Any hints or explanations would be greatly appreciated, as I'm at wit's end after 1/2 day of puzzling over this little problem!
Alex
Attachments:
time stamp data write VIs.zip ‏24 KB

Alex,
You found one of the subtle little things that can be frustrating to old-timers and newcomers alike. I did not recognize it until I read the help file (and I have been using LV since version 1.2).
First, the three characters before the commas are nulls (\00).
The reason they are there is in the help file for the Write File.vi. By wiring an array to the data input, you caused the VI to write a header telling what data format was used.
I modified your VI to simply concatenate the strings and then write a simple string to the file. I think this may be what you were after.
Lynn
Attachments:
write timestamp text line to file v3.vi ‏47 KB

Write to Measurement File: Time has minutes and seconds. Where are the hours?

Hi,
I have dynamic data acquired by Express VI: DAQ Assistant from a CompactDAQ and wired to Express VI: Write to Measurement File. In the resulting text file in the header the Date is recorded correctly in DD/MM/YYYY format. The Time field should be formatted HH:MMS.XXX but all I see is MMS.XXX. Is there a setting I should change to see the hours?
Regards,
Andrew.

Found the answer, sorry. Excel formatting issue. Not LabView after all.
Please delete this thread.
Cheers,
Andrew.

"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

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.

Time stamp to name a TDMS file

Hi:
I am using data from excel files to create a time stamp, after that,my VI creates TDMS files with this data in files with 5000 samples, also I am using time stamp to named the TDMS files, but my problem is that my first file takes the name 180000.000, How can I modify this? because I need my file´s name will be the first data from excel.
I attached my VI and two excel files, the idea is that the first file will be 84327.500 and the second will be 84740.950
Attachments:
test1.xlsx ‏150 KB
test2.xlsx ‏151 KB
testfile.vi ‏56 KB

First, let me congratulate you on taking your first steps to learning LabVIEW. If you have not already done it, I highly recommend you go through the online tutorials. You have an actual project to work on, so application of what you learn will be fairly immediate.
For your actual program issue, you need to read the data from the Excel file and convert it to a timestamp before you set your filename. The order of operation of your program is to set the TDMS file name while simulataneously reading from the Excel file. After you have already created the TDMS file, you convert the data to a timestamp and write this to your timestamp front panel control. Note that the first point you write to the TDMS file may or may not be what you think it is. It could easily be the same 180000.000 value you are using to name the TDMS file. You have what is known as a race condition. The order of operation between the read and write of the timestamp control is not known and can be variable. It is one of the reasons that you should NEVER use local variables to pass data around. Use wires. In LabVIEW, wires are the data and take the place of variables in a text base language. Front panel controls should be used only for user interace reasons. In your loop, you should wire the timestamp from its current conversion (wired into the timestamp on the front panel) directly to the TDMS write (currently wired from a local variable of timestamp).
A couple of other things. You do not need to convert your data arrays to matrices to index them. This can be done directly with Index Array from the array palette. This single primitive will replace the Array Subset, convert to matrix, and index matrix primitives.
You do not need to go through a string conversion to produce a timestamp. The Date/Time to Seconds primitive in the timing palette will do it directly. You will need to populate the cluster input.
When you posted your code, you did not include your subVIs. In the future, include all your VIs, either separately or in a ZIP file.
Finally, to solve your intial problem, use Index Array to pull the first row of data from the Excel file, then convert this to a timestamp using Date/Time to Seconds. Use this to create your TDMS file.
You may have noticed, if you do all this, you do not need your timestamp front panel control, other than as a simple monitor.
Good luck! Welcome to LabVIEW.
This account is no longer active. Contact ShadesOfGray for current posts and information.

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

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

Include time stamp in Write to Measurement file

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