Loop diagram
By Saad, practising automation engineer · Updated 2026-09-25
A drawing showing one instrument loop in full, with every signal, termination, and controller interface annotated.
Also called a loop drawing. It is not a P&ID and not a panel layout. One sheet (or a continuation set) covers one tag from the field device through the junction box and marshalling to the controller card and channel.
A typical analog loop diagram for PT-1001 shows the transmitter, cable C-F-1001, JB-01 terminals 1–2, marshalling MC-01 terminals 11–12, range 0–10 bar, and the AI channel. Multi-signal valves stay one tag with several paths.
SchematicForge generates that sheet from the IO list as PDF and native DXF. Engineer review still applies; the file is a drafting aid, not an ISA or SIL certificate.
SchematicForge uses this term in generated loop diagrams, the Loop Register, and termination lists.