Multiple PID controllers

[Mydy0325]

I am currently working on creating a Labview program for a shell and tube heat exchanger lab. I have been asked to
create two PID control loops --one that manipulates a steam valve to control the temperature of the hot feed tank and another that manipulates a valve after a pump to control the cold inlet flow rate. Additionally I have been asked to monitor temperatures and the hot feed flow rate and write everything to a file.

I have been able to accomplish everything, EXCEPT I cannot get Labview to operate two PID controllers in the same loop (or in separate ones for that matter, although that seems like it would create more lag/delay). I can get one at a time to function (both read and write) however once I add the second one, it neither reads nor writes data
for the second control, only the first. Before you look at my code, you must know that I am brand new to Labview (only been using it for a few weeks) and I probably have some unnecessary delay added to my code. Could my data flow be illogical? Would it be possible to give the attached code a quick glance?

One other thing I should mention that may be of interest: The current computer does not have any USB 2.0 ports. Could this be a problem with data transfer?

Thanks a bunch!

[nathand]

I doubt your problem has anything to do with the PID loops.  Have you probed the error wires from the DAQ functions - or put indicators on them - to see if you're getting an error?  It is possible that your DAQ device won't let you split up channels across tasks (also, it will probably be more efficient to read all the analog inputs at the same time than to do it in separate functions).