Multiple UUT Testing Over Temp - Which Thread or Process Should Control the Chamber?

Question

I am using TestStand 3.5 to write an automated system that can test up to 4 UUTs inside a temperature chamber.  If any of the UUT's fail, the user will have the option to abort the UUT test and either leave the test socket empty or add a new UUT in it's place.  Each UUT must pass 6 cycles of hot and cold testing before temperature testing is complete.  Each UUT may be in a different cycle than the UUT's in the other test sockets.  The parallel process model seems to work best due to the fact that individual UUT tests can be stopped and started at any time.
I am trying to determine which part of the software should have control over the temperature chamber.  When all UUT's have completed testing at each hot or cold interval, the chamber must be commanded to proceed to the next temperature set point.  My first idea was to have a seperate software module (or TestStand sequence) that only controlled the chamber and gave start test commands to each UUT, but a NI apps engineer told me that this would be like writing my own test engine and not taking advantage of TestStand's capabilities.  He then advised me to let whatever test socket has an index of 0 control the chamber.  I know there will always be a 0-index socket, but I am not sure which order the sockets will run (maybe it doesn't matter). 
Has anyone ever dealt with this situation before?  What is the architecture for this scenario?

Answer 1

Instead of modifying the process model you could just override the ProcessSetup and ProcessCleanup sequence file callbacks in your client sequence file (go to the edit menu and choose sequence file callbacks). Then you can just add code to the ProcessSetup to launch the new thread or execution, and then add code to ProcessCleanup to tell it to exit. Unless you want a drastically different or simpler model from what is supplied I wouldn't recommend starting from scratch.
If you don't want to add code to the client sequence then editing the existing model might be your best approach. Make sure you copy the entire TestStandModels directory from components\ni\Models into components\user\Models first and modify the version under the user subdirectory. For the parallel model you would likely want to add code to the ProcessSetup and ProcessCleanup in the model itself, or to the Test UUTs sequence itself where you want your new thread to be created and exited.
Hope this helps.
-Doug