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AutoQuiz: What Information Is Typically Included in a Loop Diagram?

AutoQuiz is edited by Joel Don, ISA's social media community manager.

This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.


A loop diagram typically includes all of the information indicated below, except for:

a) tag numbers of instruments connected to the loop as shown on the P&IDs and depicted by the loop diagram
b) conduit size and material in which the wires are run for the loop
c) wire numbers for all wires and terminal numbers for all connections depicted in the loop diagram
d) indication of the interrelation to other instrumentation loops, including overrides, interlocks, cascaded set points, shutdowns, and safety circuits
e) none of the above

Tag numbers (A), wire numbers and terminal numbers (C), and indication of the interrelation to other instrumentation loops (D) are three of the essential elements of a loop diagram. They define the "blueprint" for wiring of the components in the loop shown on the loop diagram. The size of the conduit and the material of the conduit (B) are not usually shown on the loop diagram because these items are generally not required for design review, installation, or maintenance.

The correct answer is B.

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, 2nd Edition

About the Editor
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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Image Credit: Wikipedia

Joel Don
Joel Don
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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