Read measurement file

HI!
I'm using a USB 6008 datalogger and "labview signal express". I'm logging realtime, but also "writing to file".
And I was wondering if it is possble to "read from file" into a chart or graph where all
data show at once/immediately, without starting the sequence.
Ove Unhammer

Hello,
Of course (fortunately !) it is possible to read a measurement file to display its data...
Basically, the idea it to select this file, read the whole of it (for instance untill you reach the EOF) for this you have different possibilities, the best one will depend on how you wrote the measurement file. If you wrote it with an express VI then, reading it with the appropriate express VI sounds quite sensible, no ?
If you need further help, please explain what you are using to write the measurment file and what kind of data you want to display (pressure measurement? high frequency signal? digital lines? else ? etc...) then it will be easier to advise you.
When my feet touch the ground each morning the devil thinks "bloody hell... He's up again!"

Similar Messages

Read Measurement file does not read the first channel of my TDMS file

When I try to read a TDMS file with the Read Measurement File express VI, the first channel of the data is not there. When I open the file up in excel the channel exists

Even I have the same doubt regarding Labview plss help me reading the Excel file from 23rd row and the graph should be drawn between 1st column and 8th column , from 23rd row . Here is the sample data.
Attachments:
Book1.xlsx ‏204 KB

Error filename measurement file

Hi.
In my project, I have used the Read Measurement File function to read .tdms file. When I run the program on another folder or another PC, then select Open file name an error occurred, error window appears. Although it did not do wrong program operation but It is very uncomfortable. So I hope how could this error window does not appear?
Thanks.
Solved!
Go to Solution.

Thanks for your answer - Proven Zealot.
I deleted all the Start Path and Filename. Now only the first Browser to open filename new error window appeared and notice that "Location is not available" - Access is denied. Then open filename next time isn't fail again. Error only appear once - the first read.
Attachments:
Read Measurement file.vi ‏34 KB
tdms_data.zip ‏342 KB

"read from measurement file" reads only first line of data

Hello,
I have a problem when trying to read a .lvm file through "Read from Measurements file" with the following block diagram
Problem: it reads only the first line of data from what I can see in the probe window,.
A part of the lvm file for reference.
I haven't used Labview in a long long time, I'm trying to figure out what I am doing wrong.
Thanks

Sorry meant to attach the lvm. Here it is. (Actually I had to put it in .txt because the forum wont let me upload a lvm file)
I unfortunately cannot share the full vi that record the data as I am not its owner/creator. I'll try to give as much info as I can with the relevant pictures attached, I hope it allows us to at least have an hint of where the problem might be.
(this is in a while loop)
In the stacked sequence, the other pannels are similar to the one shown here: value read fron a variable, converted to dynamic and a signal attribute is set. The "start recording" control operation is "switch when pressed".
Here are the properties of the set signal attributes
And here are the properties of the "write to measurement file"
Attachments:
NoTarget_full circle__Rx_-10-SAMPLE.txt ‏60 KB

Read From Measurement File... removes X Values of first column?

During one of our tests, two instruments were switched at the terminal by accident. I need to read in the massive lvm files, remove the wrong scaling and apply the correct scaling, while switching the values in the columns and right it all to new files. Simple right?
I wanted to use the Read from Measurement File.vi to make things easier, because the files are very large and I would like to analyze them 100 rows at a time. Some of the the files are around 1.5 Gigs in size so I need to read them in chunks.
The read from measurement file keeps removing the first column from the data! It outputs the data as a signal (dynamic data) and I have to use the dynamic to numeric array express vi. For some reason, before I even get to that point, the first column is not in the data.
No matter what settings I pick on the read from measurement express vi, the time column is removed from the data. I have checked/unchecked the "first row is channel names" and "first column is time channel" to no avail. The odd thing is that in the preview it shows the first column, as if it will read it properly... but it doesnt. Nothing I change in the settings can seems to make a difference in getting the first column, the x values, out of the file.
Below you can see the first column completely removed from the data.
This is extremely frustrating. By probing the signal out I can see the dynamic data attributes and the time column has already been removed, so I don't think that the signal to double array express vi is the problem, but I am not sure.
I am attaching my VI and a small data file to be analyzed. You can see what I mean.
The alternatives seem less than adequate. The read from spreadsheet file vi wants an offset of a specific number of characters not rows. The problem is that this is not constant between rows for some reason, when hidden characters are taken into account so I cant just set the number of characters in 100 rows and increment the offset in a loop... like I normally would. That means I might miss data or get a corrupted row.
This means that I have to use the read from text file, read how ever many characters I think a row is (over estimating a bit) then search for the newline character, find out how many chars are in that set and then offset that for the next loop iteration, all while converting each string number to a double. Talk about slow.
I have searched around and found that I am not the only one that has had this issue. This is a common thing, but no one seems to have the answer. Why can't the read from measurement file VI read all of the numbers in every row? Why cant I tell it I want a 2d array of doubles out and not a dynamic data type? It has to be something I am doing wrong.
Attached is a zip file with my VI and two data files. The "S19_A_DSI_detensioning_c.lvm" is the one generated by my VI (_c meaning corrected). "S19_A_DSI_detensioning.lvm" is the original measurement file. I hope you will pardon my messy VI, it's a quicky.
Any help you guys can give would be much appreciated.
[will work for kudos]
Attachments:
Scaling Factor Correction.zip ‏1109 KB

That is a great workaround. The help talked about putting a check next to "read lines" but for the life of me I couldn't find where to do that. I wonder what other VIs have mystery check options in the right mouse click menu. I mean normally options like those are inputs, I thought. I'm going to start right clicking on every VI I drop to see if there are options there I never realized.
I would still have to use the set file position VI and specify the byte offset right? How would I know where that is? I guess each character is a byte and I would count the characters in the string retrieved and then offset by that amount on the next iteration using a shift register?
While waiting for help, I ended up using the read from text file and using the match string to look for the new line character, and using the spreadsheet string to array vi, analyzed the files line by line. Thats just because I couldn't easily come up with a regular expression to get 100 lines. It was slow but it worked.
However, that still really doesn't answer the question of why it is impossible to get the first column with the read from measurement file express VI. Does anyone know? Is this a known bug?
[will work for kudos]

Labview 8 crashes when using Read Labview Measurement File

Hi All,
I am a new user for Labview. I installed Labview 8.0 from the CD (evaluation copy). I was just testing the sample code provided by NI. I opened the "Load from File and Display" example and I was trying to open the properties for the Read Labview Measurement File component when Labview crashed. I tried it a couple of times and everytime it happens the same way (when I double click the component or right click on it).
I am using Windows XP with all the updates done. In the Windows crash report, the application version is 8.0.0.4005.
Other problem I encountered is a missing component on the Input Palette (no DAQ Assistant present) and the Instrument I/O Assistant raises the error "Measurement & Automation Explorer or the Instrument I/O Assistant is not installed correctly. Please install these from the Labview Driver CD". For the last problem, I will try to run the Labview Driver CD, once I get it. But I am not sure if the DAQ Assistant will show up then or not.
Any ideas?
Regards,
Nick

Hello Nick,
While it is not my area of expertise, I would expect the DAQ Assistant would appear after installing the driver CD as you said you would be trying.
What caught my attention was the crash. The easiest way to resolve the crash is to delete the instance of the Read LabVIEW Measurement File on the diagram and place a new one from the Express Input palette (now called "Read From Measurement File"). In that situation, I would expect just pressing OK to accept the default configuration should work. The crash occurs in certain circumstances when the Read / Write Measurement File Express VIs are dropped from a previous version of LabVIEW and then their config page is opened in 8.0.x. This issue should be resolved in a future release, sorry for the inconvenience.

DAQ vi to perform digital write and read measurements using 32 bits binary data saved in a file

Hi
DAQ vi to perform digital write and read measurements using 32 bits binary data saved in a file
Two main
sections:
1)
Perform
write and read operations to and fro different spread sheet files, such that
each file have a single row of 32bits different binary data (analogous to 1D
array) where the left most bit is the MSB. I don’t want to manually enter the
32 bits binary data, I want the data written or read just by opening a file
name saves with the intended data.
      2)
And
by using test patterns implemented using the digital pattern generator or build digital data functions or otherwise, I need to
ensure that the
            binary data written to a spreadsheet file or any supported file type
then through the NI-USB 6509 is same as the data read.
I’m aware I can’t use the simulated
device to read data written to any port but if the write part of the vi works I
‘m sure the read part will work on the physical device which I’ll buy later.
My Plan
of action
I’ve
created a basic write/read file task and a write/read DAQ task for NI USB 6509
and both combine in a while loop to form a progress VI which I’m confuse of how
to proceed with the implementation.
My
greatest problem is to link both together with the correct functions or operators
such that there are no syntax/execution errors and thus achieve my intended
result.
This
project is one of my many assignments for my master thesis, so please i’ll
appreciate every help as I’m not really efficient with LabVIEW programming but
I prefer it because is fun and interesting if I get to know it.
Currently I’m
practicing with LabVIEW 8.6/NI DAQmx 8.8 Demo versions and NI USB 6509
simulated device.
Please see
the attached file for my novice progress, thanks in
advance for the support
Rgds
Paul
Attachments:
DIO_write_read DAQ from file.vi ‏17 KB

What does your file look like? The DAQmx write is expecting a single U32 value, not an array of I64.
Message Edited by vt92 on 09-16-2009 02:42 PM
"There is a God shaped vacuum in the heart of every man which cannot be filled by any created thing, but only by God, the Creator, made known through Jesus." - Blaise Pascal

Read LabVIEW Measurement File VI Multiple Times

I Get Error 4 When Calling the Read LabVIEW Measurement File VI Multiple Times. I've searched and found a paper on this issue. http://digital.ni.com/public.nsf/allkb/0576444C8FD4DC0F86256E83007FA540
So I have a question: Is there a way to fix this to I can still Calling the Read LabVIEW Measurement File VI Multiple Times?
Thank you.
Attachments:
Error 4.vi ‏33 KB
data.zip ‏258 KB

The paper you linked makes it very clear. The Read File Express VI cannot do what you want. Either use the low level File VIs and functions or open the front panel of the Express VI and then modify it to do what you want. Most likely the Express VI uses the low level file functions internally, but it may have a lot of extra code to handle special cases. It is probably easier to use the low level functions and you learn how to use them.
Look at the Examples under Fundamentals >> File Input and Output. Something there may do most of what you want and even if it does not, the exampels will help you learn how to use the file resources in LV.
Lynn

Data reading and writing problem? how to set " Read from Measurment File express.vi" 's readout datasize?

Dear all,
I want to use Labview to process a data.
Now I have a array in a text file.
this array is very very big. which is at least row*col = 6 * 100000;
the column size always 6,
but the row size is ramdom, some times is very big, like bigger than 65535,
when I use "read from measurement file express.vi" to read this file, the array I could get always 6*5339, I don't know why. the column size is always 5339.
and then I delete the 1st row of the array and then write into a txt file via "write measurement file express. vi", it takes a very long time. almost computer has no response. after a while, no file was creat to record the data.
is there an efficient way to process such big data file and store the processed file into a new file
thank you very much
Jack
Message Edited by weichengatech on 03-09-2006 12:00 AM

Hello,
There’s no real efficient way to read the file if you don’t
know exactly how many rows of data you have.
Your going to just have to read a row at a time and add the results to
the end of an array (granted for the clever programmers there are some more
efficient ways to do this than just with ‘build array’). I would start by asking you how much
information you know about the file and what the exact structure of it is (i.e.
is it a binary file, a tab delimited file, or a LVM file)? Could you provide a screenshot of the code
you are running? If you provide a little more information on the file structure
we might be able to contribute some additional information.
Look forward to hearing back from you-
Travis M
LabVIEW R&D
National Instruments

Read from measurement file (wrong values)

I have a VI where I save data using the ''Write To Measurement File utility''. When I open the .lvm file in the note pad I can see all the data correctly, but when I use the "Read From Measurement File" tool and try tho make a graph the data shown is not correct. Attached the .lvm file and one image of the chart that labview made using the "Read From Measurement File". If you open the lvm in the notepad you can see that the time column goes up to 22 sec. In the chart the time axis goes only up to 7,5 sec. What is going wrong??? Thanks
Ps: I changed the file .lvm to .txt to attach
Solved!
Go to Solution.
Attachments:
Chart.jpg ‏688 KB
teste.txt ‏156 KB

vitor22 wrote:
I tryed.
And how did it turn out? Saying I tried and not saying how it didn't work doesn't help me help you.
I was able to do it. But the X data wasn't correct. That is because your timestamps aren't regular spaced. So you can't use a waveform graph.
You need to use an XY graph. See the attached code for how to convert the two channels of data (time, your values) into a datatype to feed to the XY graph.
Attachments:
Example_VI_BD.png ‏49 KB

Read from Measurement File to XY on Waveform Chart

Something pretty simple that is giving me a hell of a time right now.
I've got a .lvm here that has been saved from a DAQ and has one column of numbers starting from 0.0000 - 27.0000 in very small steps. The next column is amplitudes of the signal at the given time. Now, from this LVM file I'm starting a new vi and I want to read those values as X and Y and get them onto a waveform chart. As of right now I've tried hooking up "Read From Measurement File" and tried "Build Table" but that won't want to plug into a chart. Plugging the file directly into a chart causes two very different lines to show up but is no where close to what I'm looking for.
Any tips as to how to complete this?
Solved!
Go to Solution.

Tasty,
More often than not I find Express VIs to be more trouble than they're worth. Here's an example of reading tab delimited data in from an .txt and plotting Y values versus X values on a graph. Hope it helps.
Andrew
Andrew
Attachments:
ReadData.vi ‏14 KB
data.txt ‏1 KB

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

Read from measurement file problem

Hi all,
I am using the "Read from Measurement File" VI that is built into LV8. I am reading in a .lvm file consisting of 2 columns. I cannot seem to figure out how to index each column. When tested using a a single column data file, I am able to use the index array vi to access the data successfully. The problem occurs when I have 2 columns. To get around this problem I split my initial data file into 2 single column data file, but I would prefer not having to do this. Is there anyway to avoid this?
When I read the 2D file into an array I can only index the data located in the 1st row 1st col and the data in the last row 2nd col.
The array size function results in the value "2" yet each column has 201 entries.

Attachments:
Write to LVM.vi ‏128 KB
To read LVM.vi ‏70 KB

Re-read in values in measurement file when file is updated

Hi,
I'm trying to control a power supply with labview and set the voltage. I've currently got it working reading in a measurement file and setting it to the value within the file. I'm now having the issue that I would like to update this value when the file is changed, as in read the file again when it is updated and set the new voltage. I've tried several things but if I put the file within the while loop then it reads it once and then returns 0 following the first loop. Outside the while loop it only reads the initial value.
I'm quite new to labview so any help would be much appreciated.
Thanks,
E
Solved!
Go to Solution.

You might want to explain your application a little better. Looking for a file to change to set an instrument does not seem like a good idea. Who is changing the file? How often is the file changed?
A better way might be to use a queue or notifier for setting the instrument.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

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.

Read measurement file

Similar Messages

Maybe you are looking for