Dear People,
I would like to ask for advice, and opinion about my solution for temperature controlling a water loop. This water loop is in a double wall of a vacuum chamber, its task to maintain constant temperature in this vacuum chamber wall. There is a Peltier heat pump, between the water loop and the ambient air, I can pump heat in two directions, using the range of -1 +1 Amperes for driving the Peltier module. (I use a Keithley 2010 with 4wire res. measurement to measure Platina res (PT800 in water), and Keithley 2400 as a current source)
I attached my VI (i have labview2011 and pid toolkit), and a screen-shot taken during running my VI. I spent a few days playing with PID autotune, but so far the best parameter set is what you seen on the Front panel.
I would like to ask that, do you think this approach is ok?
I think I am already close to the temperature stability what can be nominally reached with such a conventional PT800. As you can see in the attached secreenshot, the standard deviation is around 0.5 mKelvin.
Maybe I should try the PID Autotuning (Temperature).VI what comes with the toolkit? (I am still quite new in PID things)
Another note: I use the output limiter in my VI, because without it, the PID output was jumping a lot between negative and positive outputs. Since the Peltier-cooler has a natural thermal inertia (it needs a certain time after applying current to make efficient cooling in the water), it did not make any sense. It useful I guess for a heater wire, but not for Peltier...
Thanks much for giving me advice!
Best Regards,
