Ventana software support forum

I am starting to use Vensim to model industrial process controls. I found it is a very useful way to understand what is going on. I also think it is a valuable tool for learning and teaching about process controls. Anyway, I am starting by modeling a simple heating system. I need ideas to implement a simple integrator (error integrator). The model where I would like to implement the integrator can be found at :

www.gilbertojunqueira.com

Also, if anybody knows of websites out there about Systems thinking related to process controls, let me know.

Gil