Triggering Problem With GPIB

[gymboy85]

I am trying to get my VI to run (read continuously) but to collect only when a voltage input reaches a threshold. The trigger is needed in order to correlate a wavelength input to a voltage output based upon step number. I have tried to synchronize the two instruments, but  the other is run over a serial port  and after repeated failures I have settled on this method. It should generate a waveform plot in real-time and write the resulting data to a spreadsheet. It works fine without the trigger, but synchronizing two programs is only as accurate as I can start them each manually. I assumed using a shift register would work, but no I get no output.. any help would be greatly appreciated.

-KD

[James_D]

Greetings, I believe I talked to you on the phone a couple days ago regarding this issue. Part of your VI looks similar to an example I sent you. So basically the problem you're running into here is the orange line. Basically your program is taking one single measurement (measurement 2 on your front panel) and then feeding that into the next while loop. Since that value is never changed, it will constantly compare the only measurement you've taken against the 1E-6 value, so it will never trigger and will remain forever stuck in that while loop. The easiest way to see that this is the current behavior is to observe that the measurement 2 indicator is never changing. What you're going to want to do instead is remove the smaller while loop, and use shift registers in your remaining program loop to store your true/false for the case statement.

[gymboy85]

Thanks for the follow up on this issue; my frustration is slowly receding as I become more familiar with labview. My current modified VI is making progress, which is more than I can say for any of my previous attempts (will attach tomorrow). 

Thanks again for your help, 

-Kyle

[James_D]

No problem, please let me know if you run into further issues.