DDC instrumentation shown in accordance to ISA 5.1


Thread Starter


I work for an engineering firm and we do a lot of PIDs. However, I am not sure we are doing them properly. Need help representing DDC controls (HVAC) in accordance with ISA.

Let's take a typical small scale situation. I have a level transmitter that is reporting to a DDC system along with many other instruments. I understand that my level transmitter is LT. How do I represent it going to a DDC controller and also showing that it is a AI to the controller? Square box circle line through it? What does the LC represent? I mean I understand that it means Level Controller but is that the actual transmitter? I would assume not. Just not sure how to do typical DDC or BAS controls in accordance to ISA and show them represented correctly.