Closed loop

Closed loop can refer to:

• A feedback loop, often found in:
  • Control theory, where a closed-loop controller may be used.
  • Electronic circuits

(Regarding control theory: a closed-loop control system is one in which an input forcing function is determined in part by the system response. The measured response of a physical system is compared with a desired response. The difference between these two responses initiates actions that will result in the actual response of the system to approach the desired response. This in turn drives the difference signal toward zero. Typically the difference signal is processed by another physical system, which is called a compensator, a controller, or a filter for real-time control system applications.)

• PID controller, a commonly used closed-loop controller
• Closed ecological system where the system doesn't rely on matter exchange with outside of the system. The opposite being an open loop where outside material to support life is needed (eg. International Space Station).
• Sanitation system which aim at closing the nutrient and water cycle, often referred to as ecological sanitation systems or ecosan
• Reef aquarium Term refers to pulling water from one area in the tank and pumping it right back into one or more different areas in the tank to create higher flow and minimize dead spots

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