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AutoQuiz: Standard Range for Pneumatically Transmitted Signals

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

Today's 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. This question comes from the Level I study guide, Domain 3, Troubleshooting. Level I represents a professional who has a five-year total of education, training, and/or experience.

The standard range for pneumatically transmitted signals is:

a) 3-15 psig
b) 5-20 psig
c) 1-10 psig
d) 4-02 psig
e) none of the above

Industry recognized early on that for the sake of ease and safety it would be better for an operator to monitor and control processes in a more convenient and protected place. The need for transmitting the process variable to that place settled on pneumatic transmission.

They used 3-15 pounds per square inch gauge (psig) as the range. The value of using three rather than zero is to detect failure of the instrument air supply. The measurement of 15 psig is for 100%, because it is well below nominal pressures for the air supply for diagnostic purposes.

Thousands of pneumatic instruments, controllers, and control valves remain in use even today, well into the digital signal transmission age.

The correct answer is A, 3-15 psig.

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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