Keithley 236 Set constant source, make measurements over period of time

[rrp4d]

Hi - 

I have Labview 2010 on Windows XP and a Keithley 236 SMU. I am working on a program to set a constant source (in this case current) and measure the other (voltage).  I have a linear stair sweep program that works well so I decided to base it off from that. I took out the sweep measurement and just use the "read measurement". I also changed the setup driver input from sweep to DC.

So I set the current when I do the Keithley setup and just put the "read measurement" program from the device library in a while loop. However, it hangs up in the driver. I tried using the lightbulb so watch it compute and I still can't figure out what is hanging up. I have a stop for the while loop on the front panel but because it ever returns from the subvi, the stop button control is never called. 

My other idea is to make a sweep of a single point by setting the start and stop the same and putting that in a loop so it keeps going. The problem with this approach is that it will turn the source off every iteration which is undesirable. 

Hopefully this makes sense.

Does anybody have any ideas?

Thank you.

[RavensFan]

What is happening in the subVI?  Does it have some loop that is preventing it from finishing?

Post some code and we can help you figure it out, otherwise it is just a guessing game.

[rrp4d]

Sorry about that, I had intended to attach it. Here is the main vi and the subvi's and Keithley 236 SMU library.

[RavensFan]

I see a For Loop in your subVI, but that should stop executing at some point.  If the value that is being parsed out and fed into the N terminal is very high, it might seem like the VI is taking forever to run.

Have you looked into the subVI to see where it is hanging up?  Put probes on the various error wires to see if you are getting errors?