What is the difference between active and passive barriers?

 

The link below is a thread that appeared on control.com earlier this month, and may answer your question.

"http://www.control.com/sqposting_html?pid=1010155794":http://www.control.com/sqposting_html?pid=1010155794

Hope it helps!
Jennifer Powell
Editor & Moderator, Control.com

 

Active Barriers can give you a complete signal isolation between the field device and the control room equipment as they use its own power source to convert the signal and relays it back to control room or field. Commonly used
isolation techniques are Transformers and octo-couplers (called galvanic isolation). The passive barriers cannot isolate the signals from the field to the control room or vice versa. They simply have Zenar barriers and resisters
forming a network to limit the voltage and current delivered to the field.