10-24-2008 03:53 AM
Greetings,
I'm new to LabView (as in greener than green). We already have a vi that acquires I-V data from a Keithley 2400 and outputs these data as text files on a per run basis. I'm wondering if there is a way to configure the existing vi to acquire data on a schedule? I'd like not to have to come into my lab every 4 hours just to hit a button 🙂 Does anyone have any advice? Thanks!
10-24-2008 07:39 AM
10-27-2008 01:14 PM
Hi Bob,
There are a few ways to do this, but the way that I would suggest is to use the Elapsed Time VI inside the case structure. Just set the start time at 0 seconds and count up to 14400 seconds (4 hours). Then wire the time 'Timed has Elapsed' boolean output to a case structure that does whatever function you need every 4 hours. Also make sure you wire a true constant to AutoReset.
Regards,
10-27-2008 01:39 PM
I prefer to use the Time of Day functions for long time like that. Set the start time into a shift register. Once per second check if current time is greater than or equal to start time. If True, set a new start time and do the acquisition, else wait a second and check again.
This method does not require you to compensate for the time it takes your acquisition to run. In this regard the method I described above starts at a specified time of day rather than after a specified delay. The Elapsed Time VI does use the time of day internally but does not have an option for a target time rather than elapsed time.
By saving the next start time to a file, the system could be set up to resume testing after a power failure.
Lynn