Create logfile from three vis - data is sometimes missing

[OnlyOne]

Hello,

i have three measurement-vis running parallel in a loop

The three results are continuously saved in  global-array and also in a text-file.

The global-arrays has always all data but in the text-file is some data missing.

I think this is because the file is locked from one vi while the other vi wants to write his data.

What can i do here?

Something like writing data in a queue and another vi reads the queue and writes the file?

Or is there something like a "check if file is in use"-property? Then i could loop until unused before executing write?

Thanks

[leumaseoj]

Try LabVIEW synchronization VIs. "Semaphores" would help you for prioritize the events.

You can find examples along with LabVIEW which will help in how to use it.

[Yamaeda · Accepted solution]

Yes, writing data to a queue is the perfect solution. Quick for the sender, the writer writes in it's own pace and no data missing.

/Y

[OnlyOne]

I am not sure if using the semaphores would slow down my measuring.

If loop1 in the example would be my measure-vi1 and WriteToFile and If loop2 would be my measure-vi2 and WriteToFile .

Then loop2 is not exeuting while loop1 has locked the semaphore.

I can put the semaphore only around my WriteToFile-vi perhaps...

Or is this so fast that it will not be noticeable?

[GerdW]

Hi One,

use a queue to buffer all log data and just one additional loop that fetches the queue and writes to your text file.

Easy, fast, reliable…

[Yamaeda]

Sempaphores can slow down the measuring, as the loops will have to wait to get the semaphores, go with the queue. 🙂

/Y