Hi nicosub,

in addition to JazTai, maybe the application example Equipment Modules for SIMATIC PCS 7 using the example of the Chemical Industry can help. In the chapter 5.1 you can find two examples to control the level of a tank. Also you can find there a simple simulation, so that you can change some parameters of the PID and can see what happend without any consequents.

With regards
Heisenberg