analysis of waveform from tdms

[TatankaWilly]

Good afternoon everyone,

                  I am trying to do a little post test data analysis.  I am recording a LOT of data, the brunt of the data is from strain gages that can have up to 16 million samples.  I have attached my vi and a pdf of the front excel spreadsheet from my data file for informational purposes.

                The intent is to cycle through the data about every 200 samples, get a Min, Max, and Average, and save that data alongside the rest of the data.  Trying to get a quick view of summary of everything and knock down the size of the data file.  Right now it doesn't really appear to be doing anything.

                 Any thoughts or ideas will be appreciated.  Thank you.

[pep91]

Hello,

could you please send me your original .tdms file so I can make a more detailed debug?

I need also further information about what you are currently getting when you execute your code.

Regards

[TatankaWilly]

1) It doesn't stop at 'End of File'.  It continuously loops until I press the stop button.  I had expected the EOF from the file read vi to stop the loop.

2) It isn't graphing 32 seperate lines that should correspond to 300 data points that I am cycling through.  I am not entirely sure what it is actually graphing to be 100% honest.

The tach does appear to be working.  It was probably around 2500 rpm at this point in the test, and the graph looks like 335 seperate data points, give or take.

I have attached a smaller data file.  I also had to zip it in order to stay under the limit.  I have also loaded a current version of the VI.

Thanks.

[preston_johnson]

THanks for the post.  I have not had a chance to review your TDMS file or your VI.  However, here is a reference design, set-up for reading TDMS files in your choice of chunks, as well as collecting and recording DAQmx data to TDMS files.  I used this extensively, on data sets where I wanted to experiment with various analysis techniques. 

http://www.ni.com/example/31354/en/

Let us know if this is useful to you. 

[pep91]

Hello TatankaWilly,

I have found a way to stop the cycle which is even more robust than the "End of file" signal coming out the "TDMS Read" function.

Since "Number of cycles" is computed based on the samples to read in the tab "Strain", I can use it to stop the cycle too, being sure that I have read all the samples I wanted to read.

You did not display anything because you used Graph outside the loop; a good rule of thumb is to use Charts inside the loop, in order to keep track of all the data.

Attached you can find the vi with these changes. I also put an error indicator at the output of the TDMS Read function, using it as another condition which forces the loop to stop.

Hope my answer clarified your doubts and solved your problems.

Kind regards