LVM File formatting

Hello there.
I'm using the Write Measurement File-Express VI to save my measured data to a lvm file.
The thing is, that I want to change the headers in the lvm file and also change the header.
I attached a screenshot of a part of my code.
As you can see, there's one big wire for the signal, consisting of different doubles and I want to name each of them in the lvm correctly.
I also want to add the content of the string parts to the heading of the lvm file.
I already read, that there's a way to do that by conventional file I/O, without using an express vi. But I'm still a bloody beginner for LV and don't really know how to accomplish that.
Can anyone help me?
Thanks in advance!
Message Edited by rouven84 on 12-09-2008 12:38 AM
Message Edited by rouven84 on 12-09-2008 12:39 AM
Message Edited by rouven84 on 12-09-2008 12:41 AM
Solved!
Go to Solution.
Attachments:
screen.jpg ‏46 KB

Express VIs were designed to make life easier, but the LVM ones, in particular, are not that easy to modify. That said, you can change your column headers using the information in this post. You can add text information using the Comment input, but this is a single line of text. You could possibly add a Special Block, but this would require writing it to a file and then using the LVM VI to append to that file. If you are interested in pursuing the special block, check out the LVM Specification for how to construct it.
I realize I have just given a sketchy outline. If you are interested in pursuing any of the methods, let us know and we can post more details.
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Similar Messages

How do I read my wave form data back from an LVM file?

I collected a waveform and saved it using the LVM file format. I would like to read the waveform back into labview and display it with its timestamp and assigned name. The only way I could read the data back into Labview was to convert it to a number array. I figured if you could write a waveform and save all its data, you should be able to read it back rather easily. I've included my LVM file and two simple programs. The program I'm using is much larger, but these two programs are representative of what I'm trying to accomplish.
Thanks
Solved!
Go to Solution.
Attachments:
Write To LVM.vi ‏96 KB
Read From LVM.vi ‏67 KB
Test Data_08-12-11_1252.txt ‏29 KB

Hi Knoebel,
To display the waveform data, you'll need to change a couple things.
1. Open the "Convert from Dynamic Data" vi and change the Conversion to have a resulting data type of 1D array of waveform, as this is the datatype you are writing with the "Write To LVM.vi" Currently you are converting to an array of scalars here, which is why you are losing timestamp data.
2. Open the "Read from Measurement File" express VI and Change the Time Stamps to be Absolute (date and time) rather than relative.
3. If you want to display the timestamp on the waveform graph, pull up the properties window for the Waveform graph and change the Display Format to be Absolute Time for the X-axis and then check the Scales tab to be sure you have unchecked Ignore waveform timestamp on x-axes
After making the change to convert from dynamic data type to 1D array of waveform you can also probe the wire going into the waveform graph to check the t0 and dt values of the waveform as you read from file.
Lastly, if you look at the Write to LVM.vi block diagram, you will see a little red coercion dot between the waveform data wire and the Write to Measurement File data input terminal. It would be better to use the "Convert to Dynamic Data" express VI to make this conversion.
Hope this helps!
Sherrie

How do I display the next segment of an LVM file on a graph?

I have built an application which reads in an LVM file containing 16 waveforms. I am taking 1000 samples at 1kHz. The capture may last for up to 3 minutes, so I generate a sizable file. When I read this file back and display it I only get the first segment of 1000 samples (1 second). Generally this is fine, but I want to be able to select to view the other segments as well. I have been attempting to use the "Read Measurement File" express vi.
I have also tried to put the "Read Measurement File" in a while loop until I hit EOF and tied it to an "Append Signals" express vi before feeding it into the graph. This allowed me to see the last segment of my capture.
I understand that the amount of data I am trying to display would be too much for the graph, but isn't there some way I can point to a segment and display it? The perfect answer would be to grab the timestamps of the segment headers in my file and populate a listbox. (I am generating this file with headers for each segment.) Then I could scroll through the listbox and select the "second" that I want to examine. Then I need the "selected second" to display on the graph. I suspect that this is possible because I am already pulling the waveform names from the file and feeding them into a listbox so I can select which waveform(s) I want to examine.
Any Ideas?
technomage

Hi there,
Have you considered using the TDM file format instead of the LVM format? With TDM you specify parameters for your file and your channels. When you want to read data from the file you can extrac data based on those parameters. So you could construct a search that extracts the data from a particular time, or all the data that was acquired in a 10 minute period for example.
There are a few VIs you would have to become familiar with to do this (the datalog VIs are located in a palette on the File IO palette), but it would probably be easier for you to use these then to construct the file yourself and then program in all the search parameters.
Here are some resources with more information on the TDM format:
TDM Data Format
Introduction to LabVIEW Data Storage VIs
They should help you decide if you would like to use this format or stick with the LVM format.
Sarah
Applications Engineer | National Instruments | UK & Ireland

Can i open lvm file in a Pocket PC emulator?

Hi all, can i open lvm/xls file in a Pocket PC emulator? I keep getting an error msg...
Thanx!

I was wrong. It does not appear that PocketExcel will open an LVM file, at least not in Windows Mobile 2003 on my Dell Axim X50v. However, there is a fairly easy workaround, if you have a copy of Excel (or OpenOffice, which is free). Open the LVM file in Excel, save as an Excel binary (XLS) file, then drag the Excel file to your synch folder. ActiveSync will convert the XLS file to pocket Excel format on transfer. You can then open it in PocketExcel. You can use ActiveX to save directly to an XLS file, or use the report toolkit to make your life a bit easier.
It is possible that you can do this, since I am a fairly new Windows Mobile user. I tried a simple copy of the LVM file and tried changing the file extension to .txt. I could not get PocketExcel to even look at it, although, as you mentioned, Pocket Word opened it with no problem. Diving into the documentation did not help much either. If anyone else having a bit more experience has a better solution, I would love to hear it.
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LVM file time stamps - time stamps are not uniform

My LVM files do not have evenly separated time stamps. Is this by design? I want to record data from multiple channels at say 100S/s and see this in my LVM file. Ideally each of the 100 data points would be separated by 0.01s. This is not what I get.
I have tried changing the samples per second and the samples per channel inputs on my timing and read VIs but I don't get even spacing. I have figured out that the DAQmx Read VI always cuts the number of samples in the file in half. So sampling at 100S/s gives me 50 data points per second in my LVM file. Given that it cuts the points in half, I would like the spacing to be .00, .02, .04 etc., but I get this: .00, .01, .02, .03, .08, .09, .10, .11, .16, .17, .18, .19...
Is this normal or am I missing something?
HP

Unfortunately, I am not a DAQ user (the last time I really used DAQ was 7 years ago, before DAQmx was created). So, I have never seen your DAQ read issue.
LVM, on the other hand, I am intimately familiar with. Using the write to spreadsheet will almost always be faster than the LVM write. Under the hood, LVM write uses write to spreadsheet, but also handles a lot of other bookkeeping (you can look yourself by converting an LVM Express VI to a normal VI and diving into it). Your biggest issue will be saving the timestamps correctly. If you are using the waveform datatype from the DAQ read, the timestamp is included, so getting it right is not an issue. Formatting it in a text format for save is.
Precisely what are you trying to do? From you earlier post, it appeared you were taking one set of several channels of data every 10ms and writing to disk. Depending on how you use the LVM write, you may be attempting to open the file and close it at every write. This would be very slow and could account for your jitter. Saving at every data point is also very inefficient. You can stream at disk rate limited speeds (~10 - 60 MBytes/sec, depending on your hardware) if you optimize your buffer and disk write sizes. Optimum disk write size is about 65,000 bytes for Windows XP. Your data is probably far less than that.
Please post more details and code and I will try to help you more.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Read several lvm files into VI

Hello all,
I have a question about how to load several files into a VI. I have done a long measerement with a high samplerate so LabVIEW has made approximatelly 900 lvm files. I want to do two things. The first thing that I want to do, is to see chart/graph of the data with a scroll bar so I can look trough the data. The second thing that I want to do is write the same data (approximatelly 900 files) to lets say 20 files. So the samplerate is from 100 Hz to 0.2 Hz. Is that possible?
In the attachment I have put the VI that I currently have + one of the 900 files that I want to load.
Thanks in advance.
Attachments:
VI + LVM file.zip ‏556 KB

Hello Mark,
I'm a bit confused about the situation:
- Although you're talking about 900 files I only see 1 file in your attachment (as you also mentioned in the post).
Do they all have the same format/sample rate (and amount of samples) in each column?
If not, then please provide the necessary examples, because I don't see your variation of 0.2 Hz to 100 Hz sample rate based on this file.
That left aside, merging files should always be possible (up to a certain point)
- Can you also provide the code you used to generate the lvm-files?
This will give some background information.
Especially beccause I don't see any metadata available in your lvm-files.
- Graph/Chart choice:
If you only want to see all data at once, then a graph would be the solution seeing that you are not interested in the data sets while they're loading and only in the full set of data. Please do also keep in mind the size of the data set you're loading.
If you want to plot all colums in the same graphg with different sample rates per channel/column, then a good idea would be a multiplot XY Graph.
However, here you will also have to keep the data set size in mind.
Kind Regards,
Thierry C - Applications Engineering Specialist Northern European Region - National Instruments
CLD, CTA
If someone helped you, let them know. Mark as solved and/or give a kudo.

Display saved lvm file to graph with timestamp

Hi,
I'm having headache displaying my data with proper time-stamping. There are so many methods to save data. here I've decided to save it as a text delimited file format as lvm. a segment of my vi screen shot is attached. I want to use this way instead of other methods is the flexibilty it offers. I will be able to add on more data to store as I develop the vi. (So I'm storing data from DAQ assistant and my calculated values.) I attached a the screenshot of the file I read too.
I would like to use another vi to open this file and plot it to a graph/chart to display as a trending of the data acquired. Can someone pls advise mi on what is a better way for mi to do it?
Thanks alot!
Poh
Solved!
Go to Solution.
Attachments:
datalogging vi.JPG ‏82 KB
logged data.JPG ‏76 KB

Hi Krisna,
Sorry for the late reply, I was rushing to complete my project, wasn't able to reply.
Yes, I managed to solve it. Anyway I used such high rate in the DAQ assistant is to allow continous mode acqusition & use a software filter instead of hardware filter. however writing to file in this way - writing string into .lvm, max is 10 samples/sec. unless I use tdm (I'll then log everything).
I wasn't able to display proper time-stamping was due to the fact that I didn't add in the start-time timestamp that's required in displaying of timestamp in waveform. I'll not be able to go down to my lab, & my machine do not have LabVIEW, so what I can do is to extract portions of my report to share.
For the portion that I used to display graph (can be seen from the attachment), I deleted the 1st column, which is the timestamp (for spreadsheet viewing), but extracted the 1st element - the converted to DBL timestamp when I start logging in the DAQ vi (written together with the header).
This extracted (could be seen as a bunch of numbers in the lvm file) and and converted back to timestamp type and wired to build waveform block, providing the start-time of the waveform.
Next, I replace the use of chart with graph, as graph is suitable for plotting data acquired, and chart is better for run-time display of data. now it seemed to work fine for me, except for loading time may take a while for larger files.
Thanks for your participation in this thread!
Cheers!
Poh
Attachments:
display graph.JPG ‏39 KB
data.JPG ‏171 KB

Load LVM File in Matlab

How do you load an LVM file in Matlab? I used the code:
load test.lvm;
But it returns this error message
"??? Error using ==> load
Number of columns on line 10 of ASCII file ......test.lvm
must be the same as previous lines.
Error in ==> PlotM at 1
load test.lvm"
Could it be the headers in the LVM file?

Unfortunately, I am the wrong person to ask that question, since I have never used Matlab beyond a simple demo. However, I can give you some general tips that work in all the programming languages I have used.
LVM files should be small enough to read the entire file at one time. If it isn't you really need to use a different format. Read the entire file in as a text string.
Search the text string for the tag I mentioned above. Then look for the second line afterwards (search for CR/LF or whatever your line terminator is). This will give you the byte offset to start parsing the data lines
Matlab should have a function to convert spreadsheet file text strings into arrays. You can either use the data you have in memory (faster) or use a spreadsheet file read utility to read it off disk again, now that you know the offset to start reading.
Hopefully someone with some Matlab experience can chime in and help you more.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Embedded LVM file, memory map?

I am running out of memory, "No Space in Execution Regios" when I try to built my ARM 7 project. I want to determine the code size for each of my VIs in the project. Is there a LINK file?
The build process produces an Applicaiont.lvm file that contains some (all) of the mapping mapping. I found an SDK article that showed how to read the various data/structure size and mapping format but did it not describe how the VI executibles were mapped.
What is the best way to determine the size and mapping of both data and executable code for an Embedded project build?
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There is a linker output map file located at
.../<project dir>/<proj name>/<target name>/<applicaiton name>/2.0/project/labview.map

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Thank you very much!
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hi,
i need to export the table data in to xml file format. i got it through the GUI what they given.
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You can use DBMS_XMLGEN.getXML('your Query') for generating data in tables to XML format and you can use DBMS_XMLGEN.SETROWSETTAG to change the parent element name other wise it will give rowset as well as DBMS_XMLGEN.SETROWTAG for row name.
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ABAP to XML file - Formatting problem and UTF-8 requirement

Hi Everyone,
Could you please guide us on the ABAP coding required to get the proper XML file format. We have prepared the code for downloading SAP transaction data into an XML file format. However, we are stuck with an improper format as per Example 1.
The file format we get is this:
Example 1:
<?xml version="1.0"?><FDXLMDOrd><FXNHdrLp><CrtDtTm>20070613094517</CrtDtTm><MsgID>319304155</MsgID><MsgTyp>850</MsgTyp><MsgSubTyp>SALES_A</MsgSubTyp><Pr
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However, the format need to look like this as in Example 2 below.
We also need help in how to get " encoding="UTF-8"?> " as part of the file format.
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            <AutoCrtTrdParRole>0</AutoCrtTrdParRole>
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Thanks and Best Regards
Sitaraman

You could try to use the following coding:
*& Report ZUS_SDN_UC_XML_TO_UTF8_TRANSF
REPORT zus_sdn_uc_xml_to_utf8_transf.
define local data
CONSTANTS:
gc_encoding           TYPE string VALUE 'UTF-8'.
DATA:
gd_result             type string,
go_ixml               TYPE REF TO if_ixml,
go_stream_factory     TYPE REF TO if_ixml_stream_factory,
go_encoding           TYPE REF TO if_ixml_encoding,
go_resstream          TYPE REF TO if_ixml_ostream.
DATA:
gt_knb1    TYPE STANDARD TABLE OF knb1,
gd_xml     TYPE string,
gt_xml     TYPE TABLE OF string.
START-OF-SELECTION.
SELECT * FROM knb1 INTO TABLE gt_knb1 UP TO 10 ROWS
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go_stream_factory = go_ixml->create_stream_factory( ).
go_encoding = go_ixml->create_encoding( character_set = gc_encoding
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go_resstream =
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CALL METHOD go_resstream->set_encoding
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XML Transformieren
CALL TRANSFORMATION id_indent
    SOURCE     itab = gt_knb1
    RESULT XML go_resstream.
APPEND gd_result TO gt_xml.
CALL METHOD cl_gui_frontend_services=>gui_download
    EXPORTING
     BIN_FILESIZE              =
      filename                  = 'C:\temp\xml_to_utf8.txt'
     FILETYPE                  = 'ASC'
     APPEND                    = SPACE
     WRITE_FIELD_SEPARATOR     = SPACE
     HEADER                    = '00'
     TRUNC_TRAILING_BLANKS     = SPACE
     WRITE_LF                  = 'X'
     COL_SELECT                = SPACE
     COL_SELECT_MASK           = SPACE
     DAT_MODE                  = SPACE
     CONFIRM_OVERWRITE         = SPACE
     NO_AUTH_CHECK             = SPACE
     CODEPAGE                  = SPACE
     IGNORE_CERR               = ABAP_TRUE
     REPLACEMENT               = '#'
     WRITE_BOM                 = SPACE
     TRUNC_TRAILING_BLANKS_EOL = 'X'
   IMPORTING
     FILELENGTH                =
    CHANGING
      data_tab                  = gt_xml
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      file_write_error          = 1
      no_batch                  = 2
      gui_refuse_filetransfer   = 3
      invalid_type              = 4
      no_authority              = 5
      unknown_error             = 6
      header_not_allowed        = 7
      separator_not_allowed     = 8
      filesize_not_allowed      = 9
      header_too_long           = 10
      dp_error_create           = 11
      dp_error_send             = 12
      dp_error_write            = 13
      unknown_dp_error          = 14
      access_denied             = 15
      dp_out_of_memory          = 16
      disk_full                 = 17
      dp_timeout                = 18
      file_not_found            = 19
      dataprovider_exception    = 20
      control_flush_error       = 21
      not_supported_by_gui      = 22
      error_no_gui              = 23
      OTHERS                    = 24.
IF sy-subrc <> 0.
MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
             WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.
END-OF-SELECTION.
However, I like to mention that the file created from out ECC 5.0 (6.40, non-Unicode) contains a special character between the XML header and the data part (when displayed using NotePad Editor):
...xml version="1.0" encoding="utf-8"?>[special character]<asx:abap xmlns:asx="http://www.sap.com/a...
Using a HexEditor the special character (0x0A) is displayed as a dot.
Also Check with FM - TREX_TEXT_TO_UTF8
Reward Points if it is helpful
Thanks
Seshu

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Help needed while exporting crystal reports to HTML file format using java

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LVM File formatting

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