Loop diagrams are the most detailed form of diagrams for a control system, and thus they must contain all details omitted by PFDs and P&IDs alike. As we see in the Causal Loop Diagram below, a single loop number is used to identify the devices that accomplish a single specific action, usually an input and an output for P and ID control. As illustrated here, loop diagrams are a very important Instrumentation design deliverable. Mainly for a construction contractor who will install and wire all the loops. Use EdrawMax Online to create a similar-looking loop diagram for your project. The free loop diagram software comes with tons of free templates, symbols, and other diagram elements that help make a loop diagram of your preference.