How to set duration of multiple tasks

[rmalynn]

Hello all.  I am a new LabVIEW user and have a question on how to set a duration of a specific task and then initializing the start of another.  I am using an Agilent N3300A load and I would like to simulate the "power-up" of the device I am working on.  I want the code to start at 15A and then after approximately 1-2 milliseconds automatically drop down to 7A and continuously run.  I am using GPIB and have set up a code to continuously run, but have not been able to achieve my goal.  When I try to set up my timing, I can only achieve some sort of offset for each measurement.  I've been attempting to use a timing loop, but do not entirely know how those work.  Is there a simple solution that I am not aware of?  Thank you to all of you who can help.

[SteveChandler]

See this thread. It should get you started in the right direction.

[SteveChandler]

After a cup of coffee and rereading your post I see that your timing is 1-2milliseconds. I originally read seconds.

You will need LabVIEW Real Time if you want that kind of precision. But the load should have the ability to program waveforms.

[rmalynn]

Thank you for your help Steve.  The state machine set-up will certainly help with some of the other scenarios I am looking to simulate as the time periods are much longer.  I will have to look into obtaining Real-Time from someone within my company.

[SteveChandler]

Do you know if your load can be programmed to do the current transition for you? I have a Sorensen that has two programmable levels which can be set to constant current, resistance or power. You can program it to go from one level to the other after a programmable time. You can also program the rising and falling slew rates independantly. The load has an analog 0-10V input that can be connected to a function generator, arbitrary waveform generator or one of the NI DAQ cards so that you can make any current waveform you want.

Although I am not familiar with Agilent loads I would be surprised if they can not do something similar. If your load has this capability then that is definately the way to go. Even with LabVIEW Real Time you will have to consider communications latency issues especially if they are not deterministic.

[rmalynn]

Yes it does have the capability to do that.  I was attempting to use LabVIEW because it's a little friendlier than using the load to program, but I'm just going to have to suck it up and do it.  Thanks for the help, Steve