read several 2D Arrays out of lvm file

[simonbellheim]

Hello,

for my data aquisition, I join three 1-D Arrays to a 2D array. I then save several of these 2D Arrays to a lvm file, until it exceeds 500kb. Here I ues the "write to measurement" express VI. When I'm trying to read the data I encounter a problem:

the "read from measurement file" express vi, seems to only give out the first 2D Array, that is in the file! Each 2D Array holds 75 values for every channel. I checked the content by dragging and dropping the file to Excel and the notepad. I can then see all the arrays, I saved in the file, and not only the first one. I tried to adjust the options in the "read from measurement file" VI as well, but nothing seems to help.

I attached an example lvm file and my reading VI.

It would be very nice if somebody could help

Simon

[CorinneDoppmann · Accepted solution]

Hi

I'm not really sure which way you want to read out the data.

Do the different 2D Array all belong together, meaning that the 2nd array is just a continuation of the first?
If this is the case, you could select "Segment Headers">"No Headers" in the "Write to measurement file" VI.

Then, in the "Read from measurement file" select: Read generic text file, and set the parameters accordingly.

Use the "Read File now" function to test the set parameters.

Further you may have to change the indices for the Index Array in your VI.

However, this method has the obvious drawback of loosing the header information.

Alternatively, you can save the data in a tdms file, instead of a lvm file. Here the headers are handled better.

Select "One header only" in the write to measurement file. When your then read out the data, it automatically will read out all data.
And you keep the information of at least the first header.

If each 2D Array should be read out separately, you should use a different approach. Please let me know, if this is the case and I will explain further.

Kind regards,

Corinne Doppmann

Applications Engineer
National Instruments

[simonbellheim]

Hello,

thanks a lot for your help! The different 2D Arrays belong together and add up to a very long 3 collumn array. I tried to save the arrays with no headers in an lvm file, but I could only get the last one out. Then I saved them in a TDMS file with only one header and everything worked out properly.

Kind redards,

Simon