TDMS File Disappeared

[llaugher]

I am using LabView to acquire data from a shake table test. I have 17 channels (LVDTs, accelerometers, time, LED). Data are written to a TDMS file at 1000Hz. The same TDMS file is used for all repetitions of a given test. Each repetition is saved with a different group name. After each recording, the TDMS file viewer pops up to show the data. The user closes this, enters the next group name, and starts recording again.

I've been using this setup for many months without issue. After my last test, there was a problem that gave me quite a scare.

After testing, I went to open the TDMS file to check a value. I double-clicked the file (H1_50p.tdms) to open using the TDMS file viewer (excel). When excel opened, it gave an error about how the root was not found. I closed excel and went to check the directory of the TDMS file. Indeed, the file was gone now!

I did a search of C:\. Windows has some recollection of the file (see screenshot). But the file itself (with all the test data) was just gone. Fortunately, I was able to recover the data from a backup TDMS file. But I'm afraid to test again until I know the source of the problem. I've attached a screenshot and my VI.

Have you seen this before? What could be the source of the problem? The PC is old, and right now my best guess is just a disk error.

My DAQ hardware: 

Labview 2010 (I think that's the version, not at my DAQ PC right now)

SCXI-1000 with SCXI-1520 module and 1314 accessory: for LVDTs

SCB-68 : accelerometer and LED

[aputman]

This doesn't pertain to your TDMS problem but is more of an efficiency comment.

You are making a lot of copies of your array.  Everytime you create a branch, you are creating a data copy.  THe index array function is expandable to index more than one value from the array without making data copies.  Your block diagram would get a lot smaller, more efficient, and easier to read if you take advantage of things like this.  Also adding zero is pointless and a waste of time unless this is placeholder code.

[James.M]

Was the application running when you went to open the file? Could the application have a reference to the file open already when you opened it through windows/excel?

You are writing data to the TDMS reference, but the data doesn't actually get written to the file until you close the application. Maybe you opened the file that didn't have any data in it yet, so it errored out and deleted itself since it was empty. You can utilize the TDMS Flush function to help with this issue if this is the cause.

[llaugher]

aputman:

Thanks!

The zero offset / calibration constant portion is just there for setting up the LVDTs and getting them centered. You're totally right: I could just eliminate this for the actual test to improve efficiency. I'll definitely do this before the next one!

[llaugher]

James.Morris:

Yes, the application was stopped when I opened the file, but LV was still open.

Thanks, TDMS Flush looks like a really good way to make sure this doesn't happen again. I'll work on implementing it tonight.

[James.M]

If the application wasn't running, then I have to assume it was a Windows access (or saving, or magic) problem that caused your lost data. It's weird that it lost your file as you were opening it.

[Ben]

See also this thread where Data Finder will auto delte files.

Ben