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AutoQuiz: How to Minimize Electrical Interference with AC Power and DC Signal Wiring in a Control Panel

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


Today's automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program. The following question comes from the CAP study guide, Performance Domain III, System Design, Design, specify, and procure the hardware/software used in the system.

To minimize electrical interference when AC power and DC signal wiring meet in a control panel, it is BEST to:

a) use a different size wire
b) cross the wires at 90 degrees
c) run the wires parallel to each other
d) twist the AC wires around the DC wires
e) none of the above

Crossing the wires at 90 degrees will minimize the exposure of the wires to each other and therefore minimize the effects of interference. "Using a different size wire" will have no effect on the electrical interference. "Running the wires parallel to each other" will increase the exposure of the wires to each other and increase the effects of interference. "Twisting the AC wires around the DC wires" will also increase the effects of interference.

The correct answer is B, cross the wires at 90 degrees..

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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