Which vi is best to use from pid toolkit to control 8 temperature zones?

Question

Hi:
I recently bought LabVIEW 8.5 w/ PID toolkit but I can't find the "pid.vi" in its examples. Although I have never used this pid.vi, I heard  that this one is a good vi to control multiple  temperature zones. Help me if I am not searching this vi in a right way or place.  I am using NI 9264 module kit for the output power. My input is two NI 9211 thermocouple temperature module.
However my question is the same as of subject: Which vi is best to use from pid toolkit to control 8 temperature zones?
I also see in the readme file of NI 9264 that it can give a current drive of +/- 16mA for all channels. What does that mean? Since I'll be using a solid state relay which drives on 30mA/per channel.
Thanks for any help in advance.

Answer 1

Hi HopeS,
Unfortunately, PID control theory is not a simple subject, and there is no single answer on parameters, because every system differs in their response to inputs. That's why the P, I, and D parameters are adjustable. We do have a PID autotuning VI found in the same palette which will launch the AutoTuning wizard to help you get mor precise parameters once you have reasonable values to work with already. But again, you need to know a reasonable set of values to operate with for P, I, and D. Once you use the Autotuning Wizard to get new PID values, I would recommend replacing the VI with the normal PID VI and manually entering in the values you found through autotuning. Then you can use an array of all your temperatures (process variables) as the input to the VI. The "simulated" case of the Ready-to-Run Temperature Controller example you found is about as simple as it can get.
And the output of the VI is just going to be based on the mathematical transformations going on within the VI. Since you want a analog output current, you'd rescale that output if necessary and wire it into a DAQ Assistant VI (or DAQmx Write). I'm not sure I understand what you mean with not having to "play with the VIs" - this application will require some small amount of modification to fit your hardware.
Regards,
Vijay S.
National Instruments