How can I control the working time of while loop structure in the event structure?

[nguyenmanhcuong]

Hi all

My task is: Structure While Loop generates signal for 4 seconds when you press button "start generate", after that data was saved. You press button "start generate" again, and the loop does one again.

My problem is: the first pressing, the loop does exactly 4s (3,999s), but the secondly, thirdly pressing.... Elapsed time is not 4 seconds, always smaller (even ~ 0.003s). The Loop only works properly after pressing button "Exit" and launch program again.

How can I control exactly time work of Structure While Loop without pressing button "Exit".

Thank you any help!

P/S: I used Tick Count (ms) simply for viewing time of working of the While Loop. 

NMCuong

Message Edited by nguyenmanhcuong on 09-03-2009 03:12 PM

Message Edited by nguyenmanhcuong on 09-03-2009 03:13 PM

[billko]

My gut reaction is I think the loop is always performing correctly.  It's your method of elapsed time detection that is flawed.  Let me think on this...

[nguyenmanhcuong]

Hi billko

Did you run my program I attached? I'm sure the loop incorrectly works. For easy, you can increase the Time Taget to 5s, 6s, you will see the difference. Note, plz, that press the button "start generation" for some times while program running.

Thanks

Message Edited by nguyenmanhcuong on 09-03-2009 03:57 PM

[billko]

I'm sorry, Nguyen:

I have only LabVIEW 7.1 so I cannot run the VI.  😞

[AdnanZ]

You are using the Elapsed Time express VI. You will need to reset the timer every time the while loop runs. Also, I would recommend not using the while loop inside event structures. You should have a look at the Producer/Consumer Design Pattern (Events) template which can be found at File -> New..

Message Edited by Adnan Z on 09-03-2009 05:23 PM

[Omar_II]

You need to reset the Elapsed timer after the first time.

Use a shift register to pass a True into the while loop but then feed in a false in the right side shift register.

Each time you press Start generation it will reset the timer 

The times then were almost =

4.01

[Omar_II · Accepted solution]

This shows a quick fix

[nguyenmanhcuong]

OK, thank everyone. The Loop well works now.

NguyenMC